5 Aquatic Systems under Stress, c.

1000–1350

Artisan fishers played a small yet symptomatic role in medieval

commercialization, itself but a part of the historic process of European
development during the high Middle Ages. From something less than
thirty million in Carolingian times, the human population west of Russia
grew to about fifty million around 1000 CE and over seventy million by
the early 1300s. Feeding that demographic surge called for intensified
use of existing arable and massive clearance of woodland to produce
cereal grains. An increasing share of that larger food production sup-
ported growing numbers of non-agricultural settlements, first small, then
ever larger towns, dynamic nodes of the commercial revolution. What
had been insignificant urban populations increased to one in twenty
Europeans, perhaps more, by the early fourteenth century.
That Christendom’s long-acknowledged medieval experience of
growth had broad environmental impact is now generally clear.
Culturally shaped wants and needs of burgeoning Europeans pressed
upon interactive relations between medieval people and fish, some in
quite obvious ways, others indirectly reflecting known ecological pro-
cesses. What here follows can demonstrate ecosystem changes, effects on
fish species, and shifts in fisheries (the engagement of humans with local/
regional fish stocks) at the level of socio-natural sites. Much is the too
commonplace environmental history tale of human impacts on the nat-
ural world, some of which then bounce back on human activities,
whether contemporaries were aware or not.
During those same centuries autonomous European nature continued
to vary independently, itself modifying conditions for aquatic life at local
and larger scales. Fluctuations in temperature and hydrological param-
eters worked to the advantage of certain fish varieties and disadvantage of
others, including species of considerable human interest. From historical
distance the interplay between more familiar cultural and less easily
reconstructed natural forces is not easily traced. Probable interactions

183

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 184 The Catch

do not yield a single determined outcome, but suggest multiple perspec-

tives on diverse natural aquatic systems, some of which medieval people
used.1

5.1 Environmental Consequences of Demographic and

Economic Growth
What had the medieval expansion and acceleration of economic activity
to do with aquatic life? Replacement of woodlands with intensified arable
agriculture changed basic hydrological conditions both directly and by
proliferation of water-powered grain mills. Rising human numbers and
their concentration into towns added nutrients and contaminants to
watercourses, while the demand for fish as food soared. As these impacts
accumulated in each region, traditional freshwater and shoreline fisheries
visibly came under stress.2

5.1.1 Habitat Destruction

One long-familiar medieval economic trend needs mere re-articulation
in ecological terms: growing reliance on cereal food meant permanent
plowed fields replaced woodland from central Spain to Sweden and
Wales to Poland.3 Clearance of forests, which slow runoff and maintain

1
Readers who recall Hoffmann, “Economic development and aquatic ecosystems” will at
first see in this chapter extensive carry-over from that article. But decades of evolving
environmental understandings and continued research into medieval conditions have
shown that humans alone, even in the newest Anthropocene, are neither the sole
drivers nor determinants of environmental interaction. Despite the silent opacity of
most written sources, scholars must now concede that natural and cultural forces had
become well entwined long before synthetic treatment of late medieval marine fisheries
becomes possible. This must not deter efforts to trace environmental changes of
whatever origin.
2
In Regier et al., “Rehabilitation,” 87–88 (and see works there cited), fisheries ecologists
argued that “conventional exploitative development” damages aquatic ecosystems through
a sequence and synergy of excessive harvests, damming, destructive cultural practices,
organic and toxic pollution, and urbanization without regard for environmental effects.
Their ecosystem model comes primarily from comparative study of more or less modified
river systems in the late twentieth century. A longer temporal perspective on changes
humans have caused in New World marine coastal environments is laid out in Jackson,
“Historical Overfishing.” The deeper historical record here sketched generally confirms
these models, but suggests greater nuance and different specific processes. Whether in
marine or freshwater systems, the fishes first or most affected will be those ‘ecological
guilds’ with the most vulnerable habitat requirements (see Chapter 1, p. 49 above). Further
discussion of habitat issues appears in Supplement 5.1.
3
Darby, “Clearing the woodland,” is a classic and so, too, Wickham, “European forests”;
Hoffmann, Environmental History, 119–136, attempts an update.

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 5 Aquatic Systems under Stress, c. 1000–1350 185

steady streamflow, inescapably alters the pattern of stream discharge to

greater seasonality and irregularity. Rain and meltwaters run more
quickly off farmland. Larger and faster runoff more forcibly abrades
stream beds and channels, and then falling water levels leave a contracted
stream and deposits of eroded materials. One astute observer in late
thirteenth-century Alsace noted how clearance of the Vosges in his own
lifetime had caused much more rapid and dangerous runoff.4 Modern
scholars detect like sequences of medieval deforestation and flooding in
the Po basin and in central Poland.5 Biologists now also know that
unstable flow regimes make life hard for fishes. Those living in running
water must expend more energy during floods. They lose eggs and young
to winter spates and suffer high mortalities when small streams dry up in
summer. Species which spawn in flooded margins are adapted to con-
sistent seasonal patterns of rising and falling water, so instability disrupts
their reproductive behaviour.6
Soil erosion and alluvial deposition is becoming a well-known conse-
quence of medieval agricultural expansion. First the natural vegetative
cover was removed. Then characteristic medieval farming practices dis-
rupted the soil surface and its structure. Plowmen drove long straight
furrows or pulverized the soil to prepare for autumn sowing of winter
grains. Bare fallow stripped all plants from a third or a half of arable
almost year-round. Large open fields broke neither wind nor water nor
the creep down slopes of the soil itself. All this let topsoil flow to the
watercourses, especially during heavy winter rains and snowmelt.7 In the
Leine valley of Saxony, where during the 780s and 790s Frankish con-
queror Charlemagne had promoted new rural settlements and
clearances, large sediments from eroded topsoil overlain with former
subsoil yield radiocarbon dates between the 790s and 850s. Across the
entire lower Rhine valley a major pulse of sedimentation set in around

4
Writing about 1300, a Colmar Dominican compared his own times with the less-
developed Alsace his fellow friars had entered a century before, including “Torrentes et
flumina non ita magna tunc sicut nunc fuerunt, quia radices arborum fluxum nivium et imbrium
per tempus in montibus retinuerunt.” (Jaffé, ed., “De rebus Alsaticis,” 236).
5
Fumagalli, Landscapes, 110–121. Dunin-Wąsowicz, “Natural environment and human
settlement,” 94–95 and 102, refers to “great changes in the hydrographic balance [viz. of
Central Europe], which reached proportions of a natural disaster during the course of the
13th century.”
6
Compare Hynes, Ecology, 327–332, and the different habits of “white fish” and “grey fish”
in Regier et al., “Rehabilitation,” 93–96.
7
A point emphasized in both Vogt, “Aspects of historical soil erosion,” 86–88, and Bell,
“Archaeology under alluvium,” 272. For a global perspective see Hoffmann et al.,
“Human impact … during the Holocene.”

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 186 The Catch

1000 CE.8 In southern England, where woodland clearance got under

way in the eighth century and was complete by the eleventh, erosion and
deposition rates in the river Nene and the upper Thames accelerated
from around 800 to reach in late Saxon and early Norman times all-time
maxima tenfold their prior Holocene average.9 Among the hills of
Dauphiné about the year 1000 farmers pioneered the wooded shores of
Lac Paladru; their new grain fields quickly produced higher rates of
erosion now visible in well-dated lake-bottom sediments suddenly full
of loam from plowed topsoil and organic waste from cattle.10 At the crest
of medieval expansion in the early fourteenth century, researchers both
along the French Alps and across central Europe find unusually heavy
erosion episodes when climatic change brought heavier precipitation to
precisely those landscapes most recently deforested and intensively
plowed for maximum output of cereal grains.11 Incrementally, region
by region, watershed by watershed, surges of hydrographic instability,
soil erosion, and deposition followed pulses of local conversion of wood-
lands to arable.
Soils from upriver washed down to the estuaries. The Oude Rijn
mouth of the Rhine in Holland silted shut by the eleventh century, and
between the thirteenth and sixteenth centuries the expanding delta of the
Wisła filled in the one-time bay between Gdańsk and Elbląg.12 Long
unavailing struggles of Bruges against plugging of the Zwin, and of
Ravenna against filling of the Po delta are historical commonplaces.13

8
Nitz, “Feudal woodland colonization,” 178; Hoffmann et al., “Trends and controls of
Holocene floodplain sedimentation.” A more general view of the process is in Wickham,
“European forests,” 534, and works there cited.
9
Lambrick, “Alluvial archaeology,” 222; Williamson, Shaping Medieval Landscapes,
169–173; and with such regional studies synthesized in Lewin, “Medieval
environmental impacts,” 277–280 and 294–299. Note the temporal coincidence of
these destructive impacts on English rivers with the so-called fish event horizon there
(Chapters 2 and 4).
10
Colardelle and Verdel, eds., Chevaliers-Paysans, 31–32, and Colardelle and Verdel, eds.,
Les habitants, 57–60. Pollen analysis finds cultivated plants and field weeds in the new
sediments. Bertrand and Bertrand, “Pour une histoire écologique,” 74–80, think this a
common phenomenon in France during central medieval centuries.
11
Bravard, “Des versants aux cours d’eau”; Bork, Bodenerosion und Umwelt; Bork et al.,
Landschaftsentwicklung, 221–226 and 237–249; and Bork and Schmidtchen, “Böden:
Entwicklung, Zerstörung.”
12
TeBrake, Medieval Frontier, 70 and 147–148; Filuk, “Biologiczno-rybacka
charakterystyka ichtiofauny,” 146–148.
13
Large areas in peninsular Italy and other parts of the classical Mediterranean had,
however, already suffered enduring damage from deforestation, overgrazing, and
erosion followed by coastal deposition in Roman times (Hughes, Pan’s Travail, 90 and
190; Hughes, Mediterranean, 39–44 and 54–57), so further changes during the Middle
Ages (as for instance at the mouth of the Tiber) were less dramatic there. Nevertheless
Ortolani and Pagliuca, “Cyclical climatic-environmental changes,” summarize local

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 5 Aquatic Systems under Stress, c. 1000–1350 187

For some fish species, this could mean loss of important migratory,
spawning, and juvenile habitats. Heavy silt loads make water more often
turbid, reduce light penetration, and can smother fish or prey species
adapted to live in weed or gravel beds. Like the more dramatic alterna-
tion of floods and low water, the effects favour certain species relative to
others. A tenth-century monastic chronicler at Novaliense in the Italian
Piedmont was well aware that clear mountain water held lots of fish and a
muddy stream few.14 Soils from unstable cleared lands in tenth–twelfth-
century Sicily went down local rivers to trigger shifts in their fish
populations.15
To process the new grain supplies a little-used late antique invention,
the watermill, surged across the medieval landscape. From perhaps a
couple hundred in King Alfred’s England, they multiplied to 5,624 in the
Domesday Book of 1085. In Poitou, Berry, Languedoc, Burgundy, and
Lorraine mills proliferated from the tenth century through the twelfth.
On the Aube, where fourteen mills are recorded in the eleventh century,
sixty-two may be counted in the twelfth century, and almost two hundred
in the early thirteenth. Then and later their construction became a
normal part of rural development in the Egerland and in central Silesia.
Late thirteenth-century Milanese writer Bonvesin de la Riva estimated
the territory of his city held 900 mills running about 3,000 wheels.16 One
historian of technology summed it up this way:
By the close of the Middle Ages watermills were in use on streams of every type.
They dammed up the rivers of medieval man; they were on the banks of his
brooks and creeks, in the middle of his rivers, under his bridges, and along his

investigations identifying alternation between accelerated stream erosion during wet

periods (the earlier and the later Middle Ages) in the Po basin and accelerated wind
erosion in Sicily during warm dry periods (eleventh–thirteenth centuries).
14
Written about 926, the Chronicon Novaliciense, III, viii (see Montanari, L’alimentazione
contadina, 284), remarked on the difference between two alpine streams, one flowing
into Italy, “semper turbida, paucos ferens pisces”, and its neighbour (the Durance) bound
for Provence, “valde pisciferam et claram.”
15
Bresc, “La pêche dans l’espace économique,” 274–275.
16
Reynolds, Stronger Than a Hundred Men, 47–69, remains a major and still not superseded
overview, but its normative enthusiasms should be balanced with more recent or regional
studies such as Benoit and Rouillard, “Medieval hydraulics in France,” 169–180 and
203–213; Devailly, Le Berry, 226–227; Maas, Moines-défricheurs, 71–74; Durand,
Paysages médiévaux, 253–258; Durand, ed., Jeux d’eau; Richard Holt, Mills of Medieval
England, 107–144; Langdon, Mills, 8–64; Rynne, “Waterpower in medieval Ireland”;
Muggenthaler, Kolonisatorische und wirtschaftliche Tätigkeit, 129–130; Cnopf, Entwicklung
der Teichwirtschaft, 9–23; Dembińska, Przetwórstwo zbożowe w Polsce, 63–175; Podwińska,
“Rozmieszczenie wodnych młyno,” 373–402; Hoffmann, Land, Liberties, and Lordship,
261–262; Bonvesin de la Riva, De magnalibus Mediolani, lib. IV, 14 (Chiesa, ed.,
pp. 114–117); Squatriti, “Advent and conquests” and Water and Society, 126–144;
Muendel, “Grain mills of Pistoia” and “Mills in the Florentine countryside.”

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 188 The Catch

coastlines. They impeded navigation and created streams (in the form of mill
races and power canals) and lakes (in the form of storage reservoirs behind
waterpower dams) where none had existed before.17

In fact, as remarked in Chapter 1, stream ecosystems had long existed in

most of Europe, but less often ponds. Medieval watermills commonly
drove their overshot or breast wheels by using a dam or weir two to five
meters high to concentrate the falling water and pond a reserve supply of
it. Medieval millwrights learned to do this on ever larger rivers. Once a
design was in place at a location, it rarely changed.18 Dams blocked
running water and created still water: each of the nineteen mills erected
during the Middle Ages on the forty-kilometer-long Skrwa, a Masovian
tributary of the Wisła, had a dam about three meters high and a pond
covering up to ten hectares.19 As moving water slows, it drops the solids
it has carried in suspension. On the Derwent in the English Midlands
two meters of gravel and silt alluvium eventually covered a one-meter
timber mill dam, gate, and race dated by dendrochronology to the mid-
twelfth century.20 The broad surfaces of standing waters absorb more
solar energy. This both warms the water and further improves conditions
for growth of rooted plants. In twelfth-century Picard charters and con-
veyances slower, deeper, and weedier waters backed up behind mill dams
and weirs all along the Scarpe, the Oise, and the Somme.21 Ubiquitous
watermills formed and multiplied a new kind of aquatic habitat, one to be
probed more deeply below.
On existing watercourses and their native fish populations mills had
immediate effect, for they blocked movement of migrants. Like the

17
Reynolds, Stronger Than a Hundred Men, 69. Compare Lewin, “Medieval environmental
impacts and feedbacks,” 291–293.
18
For technical particulars and their implications, see Lucas, Wind, Water, Work, whose
focus is industrial applications of milling power, and the essays in Walton, ed., Wind and
Water, whose contributors have more social interests. Langdon, Mills, 70–107, shows
breast and overshot designs dominating England by the late twelfth century and Benoit
and Rouillard, “Medieval hydraulics in France,” 203–208, the same for northern
France, although undershot wheels were there more common in flat terrain and
horizontal wheels remained a tradition in certain Mediterranean areas and also Ireland
(Rynne, “Waterpower in medieval Ireland,” 9–40). Nevertheless, Chiappa Mauri,
I mulini a acqua nel Milanese, 152–175, emphasizes an early medieval replacement of
horizontal with vertical wheels, and Sicard, Moulins de Toulouse, 38–43, documents a
shift from mills on anchored rafts to land-based mills with dams or weirs.
19
Brykala, “Watermills’ functioning.”
20
Clay, “A Norman mill dam,” and works there cited. Compare Bagniewski and Kubów,
“Średniowieczny młyn wody,” and other medieval Polish mills described in Dembińska,
Przetwórstwo zbożowe, 90–135.
21
Fossier, La terre et les hommes en Picardie, 366–368, 380–389, and 395–397. Compare
findings by Walter and Merrits, “Natural streams and the legacy of water-powered
mills,” of extensive siltation behind preindustrial mill dams in eastern North America.

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 5 Aquatic Systems under Stress, c. 1000–1350 189

concentrations at natural barriers, those at dams and weirs offered fishers

profitable access to migratory species. The contemporary biographer of
St. John of Metz (Gorze, d.974) actually thought his monks’ need for fish
was why he built mill dams. Even deep in central Saxony, operation of a
salmon trap at the mill dam at Lauenheim on the River Zschopau fueled
a century of dispute (1293–1393) between Altzelle abbey and the von
Steinbach family.22 Possession of mills was associated with the right to
take eel on the Duero in Castile, the Garonne near Toulouse, the Meuse
around Liege, and in the early fourteenth-century psalter illuminated for
Sir Geoffrey Luttrell of Lincolnshire (revisit Figure 3.7).23
But impassable barrier dams kept migratory species from vital
spawning habitat. Blocked runs of fish – were they trout or shad? –
ascending the Sarca from Lake Garda in 1210 caused the bishop of
Trento, who held sovereign fishing rights in that county, to require
removal of mill dams at Arco.24 For the sake of the salmon Scottish king
William (1165–1214) established judicial precedents requiring all dams
and weirs be fitted with a permanent mid-stream opening and all barrier
nets be lifted from each Saturday evening until Monday sunrise.25 An
English law book from the 1290s, Fleta, likewise acknowledged that mill
dams could damage established fisheries.26 Dutch historical ecologists
have most recently argued from sparse medieval and early modern
salmon price series as well as material evidence at prehistoric and medi-
eval sites for a correlation between construction of water mills in the
Rhine basin and the first declines of salmon populations there. Others
have asserted that eleventh–twelfth-century dikes built to drain marshes
suppressed sturgeon stocks in the Rhine delta.27 Impassable dams are
well known to break the ecological continuity of rivers and fragment even

22
Pertz, ed., “Vita Iohannis,” MGH, SS, 4: 362, “cum molendinis fluminibus causa piscium
obcludendis”; Beyer, Cistercienser-Stift und Kloster Alt-Zelle, charter nos. 216, 510, and 518.
23
Perez-Embid Wamba, El Cister en Castilla y Leon, 137–138 and 178–179; Mousnier,
L’Abbaye de Grandselve, 189–190; Sicard, Moulins, 118–128; Derveeghe, Domaine du Val
Saint-Lambert, 63–66; Luttrell Psalter, fol. 181r.
24
Stolz, Geschichtskunde der Gewässer, 346.
25
Hoffmann, “Salmo salar in late medieval Scotland,” 362–363, and sources there cited.
The so-called Assizes of King William, art. 10, described the requisite opening as “so
large that a well-fed three-year-old pig could turn about without touching its snout or its
tail” (in tantum quo unus porcus trium annorum bene pastus est longus, ita quod neque grunnus
porci appropinquet sepi nec cauda . English counterparts occur in Wright, Sources, 91, and
Winchester, Landscape and Society, 111.
26
Fleta, III, 110–114. Those mills and mill leets on the Garonne at Toulouse also damaged
the fishing (Mousnier, La Gascogne Toulousan, 115). On the other hand, as in the early
modern Elbe, flood events could break downstream barriers and allow the return of
salmon to upriver fisheries where they had long been rare or absent (Wolter, “Historic
catches”).
27
Lenders et al., “Historical rise of waterpower”; Boddeke, Vissen, 169–176.

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 190 The Catch

populations of resident fishes, while other modern research indicates a

succession of even modest two- to ten-meter barriers has cumulative
negative impact on upstream populations of migrants.28 These losses
mattered because, ecologists agree, the spawning environment in fresh
water determines the productivity and survival of anadromous fish.29
Turning from rural development to other aspects of the medieval
economy, human population growth and urbanization in the typically
organic-based preindustrial resource system affected both water chemis-
try and hydrological conditions for aquatic life. Waste from more and
larger human concentrations, from rural monasteries to towns of twenty
or even fifty thousand, necessarily increased the nutrient load – i.e.
soluble nitrates – in watercourses.30 The several hundred monks and
lay brethren at early thirteenth-century Clairvaux were served by a diver-
sion of the Aube river, which ran through gardens, mills, brewery, fulling
mill, tannery, laundry, and latrines before rejoining the main stream.31
Such point source pollution also typically flowed from elite lay resi-
dences.32 Local streams likewise received the human, animal, and craft
waste of towns, whether by runoff from street disposal (even with inten-
tional diversions to flush gutters as at Milan, Strasbourg, and Goslar), by
purposely emptying the contents of cesspits into flowing water below
town (Köln), or by direct siting of latrines over watercourses (Rouen,
Nürnberg). If, as inhabitants of the Terra Firma legitimately jibed,
“I Venexian caga in aqua,” there was yet another source of nutrients for
the lagoon.33 No wonder contemporary Italian doctors and dietitians

28
See discussion in Jungwirth et al., “Re-establishing and assessing ecological integrity”
and the comparative survey of French river systems in Merg et al., “Modeling
diadromous fish loss.”
29
Schalk, “Structure,” 222–224. For extended discussion of anadromous issues see
Supplement 5.1.1.
30
Grewe, “Wasserversorgung,” 75, cites nineteenth-century calculations of an annual
preindustrial per capita output of 34 kg of feces and 428 kg of urine, totaling 462 kg of
nitrogen-rich excrement. The daily adult output estimated by Leguay, L’eau dans la ville,
123, totals 47.5 kg of human fecal matter and 360–550 kg of urine per year.
31
“Descriptio … Claraevallensis.” Monastic effluents are left untreated in Lillich’s classic
“Cleanliness with godliness” and by Magnusson, Water Technology, 98–101, but get
more attention from Kosch, “Wasserbaueinrichtungen in hochmittelalterlichen
Konventenanlagen,” notably pp. 96, 110–112, and 134–135, and Benoît and Wabont,
“Wasserversorgung in Frankreich,” especially pp. 195, 204, and 207–216, which include
orders besides Cistercians.
32
Grewe, “Wasserversorgung,” 74–75; Benoît and Rouillard, “Medieval hydraulics in
France,” 180–187.
33
Grewe, “Wasserversorgung,” 75–80; Dirlmeier, “Die kommunalpolitischen
Zuständigkeiten und Leistungen”; Frieser, “Abwasserkanäle und heimlichen
Gemächer Nürnbergs”; Lachmann, “Die Gewässer und ihre Nutzung,” 311–315; La
Casva, Ingiene e Sanità di Milano, 64–66; Guillerme, Age of Water, 105–107; Leguay,
L’eau, 247–275; Leguay, Pollution, 16–32. Crouzet Pavan, “Les eaux noires,” details the

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 5 Aquatic Systems under Stress, c. 1000–1350 191

doubted the wisdom of eating fish from waters polluted with urban
effluent.34 But Robert Guillerme has argued that organic acid- and
alkaline-based processes used by early medieval textile and leather crafts
caused “the precipitation of solid organic materials in water which river
currents carried beyond city limits.”35
And what was downstream? One introductory fish tale has already told
of Constance’s pollution of its lakeshore with urban wastes. Along what
was London’s little river Fleet, sediments from a human generation or
two of the mid fourteenth century show loss of molluscs requiring clean
water and appearance of diatoms typical in dirty water.36 Excavations in
the bed of the Pegnitz below medieval Nürnberg recovered late medieval
butchery waste and household refuse, findings which corroborate the
stream’s foul repute when each summer’s low water left it long
unflushed. By the early 1400s Parisian effluent was likewise making the
Seine below town “infectée et corrumpue” every summer.37 All are
symptoms of aquatic ecosystems under stress.
Nor, despite Guillerme’s optimism, did medieval industry merely add
nutrients. More immediate toxic effects came from crafts such as slaugh-
tering livestock, tanning, or extracting fibers from flax and hemp by wet
decomposition (‘retting’). When the latter activity killed fish near Douai
in 1452, holders of fishing rights sued a clothier for damages.38 Brewers,
fishers, and ordinary consumers at Colchester in 1425 complained that
the tanners and tawers caused the “impayring and corrupcion” of the
river Coln and “destruction of the ffysche therynne.”39

problems Venetian authorities faced in expelling human waste from urban waters into
the lagoon.
34
Nada Patrone, Il cibo, 339–340. Species and stable isotopes found in fish remains from
sites near Basel suggest increased nutrient loads and contamination in the fourteenth-
century Rhine (Häberle et al., “Carbon and nitrogen isotopic ratios”).
35
Guillerme, Age of Water, 97–100.
36
Schofield and Vince, Medieval Towns, 213. Regier, “Rehabilitation,” 88, specifies the
latter botanical phenomenon as characteristic of an aquatic ecosystem under stress.
Where current speed and substrate prevent establishment of rooted aquatic vegetation,
larger nitrate loads encourage suspended algae to grow and increase turbidity. Jørgensen,
“Local government responses,” highlights authorities’ efforts to mitigate contamination
in rivers.
37
Frieser, “Abwasserkanäle,” 194–195. The Seine was so pungently described in a royal
ordinance against waste disposal from 1415 (Isambert et al., eds., Recueil général des
anciennes lois, vol. 8, p. 565, cap. 683).
38
“Et ont esté si puantes et infectés que les puissons qui estoient es yauwes de mesdis seigneurs sont
aulcuns et en grant nombre mors et les autres espars au loings en estranges yauwes,” Leguay,
L’eau, 292, citing Plouchard, “La Scarpe et les gens de rivière,” 850–851. Amacher,
Zürcher Fischerei, 96, reports a similar fish kill in 1466.
39
Gimpel, Medieval Machine, 86, quotes from Page and Round, eds., Victoria History of
Essex, vol. 2, p. 459, and further mentions thirteenth-century archival regulations against
letting any tanning waste flow into Marseilles harbor. More fish kills occur in Guillerme,

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 192 The Catch

Toxic heavy metals emitted from medieval mining and metallurgical

processes still contaminate substrates, riverbanks, and floodplains in
widespread European watersheds. Even now lead concentrations in
waste deposits from medieval mines in the Pennine headwaters of the
Tyne, Don, and Ouse as far downstream as York exceed those of Roman
or modern industrial dates.40 Maximum contamination in lakes and
shorelines of the Harz and the Staufer basin of the Schwarzwald from
tenth- through thirteenth-century processing of copper, lead, zinc, and
cadmium is as much as ten times the modern legal limit.41 Alas, I know
of no analyses for heavy metals in medieval human or fish remains from
these and other affected regions, but studies of human skeletons else-
where clearly indicate generally high lead exposure among especially
European urban populations of high and late medieval date. Even the
avid sixteenth-century mining promoter Georg Agricola had to admit to
the deadly consequences of mining and refining.42
Activities in the urban and commercial sector further impeded the free
flow of water. Since the eleventh century castles and towns had diverted
rivers to fill defensive moats; this stratagem gained popularity in the later
Middle Ages.43 Accessible markets for fuel drove extensive peat-digging
which created the Norfolk Broads, smaller but more numerous plassen in
North Flanders, and South Holland’s vast but equally anthropogenic
Haarlemmermeer between Haarlem and Leiden.44 And between the
eleventh and fourteenth centuries still more weirs, dams, and ponds,
were built to power new industrial operations like malting, fulling,
metal-working hammers and bellows, sawmills, and paper-making.45
The type and scale of physical and chemical changes which medieval
economic development brought to European inland waters most directly

Age of Water, 152; and Heine, “Umweltbesogenes Recht,” 123. Sawmill waste harming
fish was an object of 1504 legislation in Tyrol (Stolz, Geschichtskunde der Gewässer,
381–383).
40
Passmore and Macklin, “Geoarchaeology of the Tyne”; Hudson-Edwards et al.,
“Mediaeval lead pollution”; Macklin et al., “Pollution from historic metal mining.”
41
Goldenberg, “Frühe Umweltbelastungen”; Diecke, “Findings.” Mining and smelting
waste in the Valle d’Aosta are in Di Gangi, L’attivita mineraria, 81–92, and Tumiati,
“Ancient mines of Servette.” Claustres, “Mining legacy in French Pyrenees,” reported
lakes with lead concentrations in medieval layers greater than those of the
nineteenth century.
42
Jaworowski et al., “Heavy metals in human and animal bones”; Rasmussen et al.,
“Comparison of mercury and lead levels”; Agricola, De Re Metallica, 5 (tr. Hoover,
p. 8).
43
Guillerme, Age of Water, 47–50 and 118–131.
44
Lambert et al., Making of the Broads; Borger, “Draining–digging–dredging,” 153–157;
Dam, “Sinking peat bogs,” and Dam, Vissen in veenmeren, 58–81.
45
Reynolds, Stronger, 69–97; Benoît and Rouillard, “Medieval hydraulics in France,”
208–214.

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 5 Aquatic Systems under Stress, c. 1000–1350 193

and heavily affected small- and medium-sized watercourses. Brooks,

streams, and small rivers are by their very size, high ratio of surface area
to volume, and abundance in the landscape more closely tied than large
rivers to their immediate terrestrial environments. Removal of bankside
vegetation; local ditching, diversion, or embankment; small mill ponds
and dams; and effluents from concentrations of livestock or humans have
profound local impact, removing the whole waterway from its natural
form and sources of energy. Large rivers, in contrast, are linked to their
surroundings through their multiple channels and extensive floodplains,
so simple and local changes in riparian conditions have less effect.46
Hence the impact of preindustrial economic development differed in
degree and kind from that of industrial development. Yet the finding
should not be oversimplified. The much-studied Rhine and its major
tributaries, for instance, are said to have suffered little from human
activity before channelizing and embanking in the early nineteenth cen-
tury began a total degradation.47 But most studies of major European
rivers proceed from a present and retrospective standpoint with little
deeper historical knowledge or awareness. The evidence of medieval
landscape change is overwhelming. Watersheds are systemic continua;
what enters at the top flows all the way down. Besides dams cutting off
what had once been the highest spawning sites, medieval deforestation
and erosion must be acknowledged a principal cause of more erratic flow
regimes and contributor of material to the many mainstream sandbars
and islands known from early modern records.

5.1.2 Perceptions of Overfishing and the Evidence of Depletion

For many past and present observers fishing is the most obvious and
understandable human impact on local and regional aquatic ecosystems.
Medieval efforts to satisfy demand for fish as food rose with and beyond
rising human numbers. Widened adherence to Christian food rules
encouraged fish consumption. We have seen the growth and operation
of urban fish markets all across medieval Europe. Such markets and the
professional fishers who supplied them were by the thirteenth century
held mainly responsible for rising exploitation of fisheries in northern
Flanders.48

46
A general comparative point made in Regier, “Rehabilitation,” 88–89.
47
Lelek, “Rhine River”; Cioc, The Rhine, 21–75 and 145–171. Or are modern historians as
well as biologists susceptible to a form of shifting baseline syndrome?
48
Materné, “Beroeps- en vrijetijdsvisserij,” 142–144. Subsequently Van Neer and
Ervynck, “New data on fish remains,” 225, argued that the relatively greater reliance
on marine fish in the diets of late medieval Belgian towns as compared to rural castles

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 194 The Catch

Populations of fishes which Europeans liked to eat came under evident

stress. One sign is contemporary awareness of damaged resources, com-
monly conceived as overfishing. A remarkably explicit early articulation
prefaces the first full-scale fisheries ordinance issued by French King
Philip IV in 1289:
… today each and every river and waterside of our realm, large and small, yields
nothing due to the evil of the fishers and the devices of [their] contriving, and
because the fish are prevented by them from growing to their proper condition,
nor have the fish any value when caught by them, nor are they any good for
human consumption, but rather bad, and further it happens that they are much
more costly than they used to be, which results in no moderate loss to the rich and
poor of our realm …49
Philip’s remedy is examined in Chapter 6 below. A more particular case
of fishing pressure is reported from the Pinzgauer Zellersee, high in the
Salzburg Alps. Its rich fisheries drew a mid-fourteenth-century settle-
ment of professionals, who paid the archbishop 27,000 whitefish and
18 lake trout a year for the right to take, smoke, and sell still more. After
one human generation the whitefish catch collapsed, and replacement
stockings of pike ate nearly all the trout, so the fishing community
determined to rest the lake for three years and then to fish only with far
fewer nets in a limited season and a restricted area.50
By the late fourteenth century petitioners blamed weir fishing for
decline of salmon and sturgeon in the Thames estuary, and English
coastal fishers a generation later conceded they had depleted local
stocks – to excuse, it should be noted, their illegal fishing elsewhere.51
About the same time Siena legislated against overfishing in the lagoon of

and monasteries marks the reduction of fish populations near those urban
concentrations
49
Cum omnia et singula flumina necnon et riparie magne et parve regni nostri per maliciam
piscatorum seu excogitata ingenia sint hodie absque fructu, ac per eos impediantur pisces crescere
usque ad statum debitum, nec sint alicujus valloris quando ab eis capiuntur, nec etiam prosint
humano usui ad vescendum, immo pocius obsint, et inde accidit quod sint multo plus solito
cariores, quod cedit in dampnum non modicum tam divitum quam pauperum regni nostri …
Duplés-Agier, “Ordonnances inédites,” 49. Jeulin, “L’élaboration par la monarchie,”
observes how these themes became a commonplace of French legislation. Further
discussion in Rouillard, “La législation royale.”
50
Freudlsperger, “Kurze Fischereigeschichte,” 100.
Diagnosing overfishing from evidence of fishing and fish shortages does betray aspects
of circular reasoning, but the assertion in Jäger, Einführung, 192, of no evidence for
decline in numbers of aquatic organisms before the 1500s rests on the unrealistic
assumption that only governmental records of catches constitute “scientific” and hence
credible data.
51
Wright, Sources, 91, cites an unpublished Plea and Memoranda roll of 1386; Given-
Wilson et al., eds., PROME, Henry V, 1416 March 16, membrane V, 33, X (Rotuli
Parliamentorum II temp. Hen. V, vol. 4, 79).

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 5 Aquatic Systems under Stress, c. 1000–1350 195

Orbetello and authorities at Santander tried to deter local depletion by

taxing nearshore catches.52 Perceptions of damaged resources were by no
means confined to inland waters.
Less subjective indicators allow closer description and diagnosis of
localized fish stocks under stress. Our opening tale of the sturgeon
revealed a steady reduction in size of those eaten at tenth- through
thirteenth-century Gdańsk. Like trends are more vaguely visible in some
other large central European fishbone assemblages predating 1200.53 At
Abbeville on what was initially the Somme estuary the share of large adult
flatfishes at excavated sites fell from the twelfth century to the early
fourteenth, while that of small, mainly immature, specimens rose. Those
reciprocal trends reversed after mid-century human population losses, but
had resumed by 1500.54 As someone in the entourage of Philip IV already
seemed to know, shrinking average size indicates a stock where more fish
are being extracted before reaching their full growth.
Shifts in species composition of medieval catches are still more telling.
Investigators have diagnosed a decline of anadromous and cold-water
varieties during the high and later Middle Ages in several regions of
western Europe. Here our sad introductory tale of the sturgeon needs
only brief review. Zooarchaeologists studying Baltic sites concur in the
steady decline not only in size, but in numbers and relative frequency of
this taxon between the seventh/ninth centuries and the twelfth/thirteenth
and point to overexploitation (Figure 5.1). Records around the North
Sea trace a diminishing presence, too, although some observers argue
more for loss of habitat. The European sturgeon may better have sur-
vived in the long-fished Mediterranean, although market price lists less
and less often included it. From a common though costly food item,
sturgeon everywhere became a rare symbol of prestigious luxury.
Atlantic salmon, like sturgeon, long served to display a host’s high
status as ubiquitous features of conspicuous consumption at festive elite

52
Rombai, “Le acque interne … Maremma,” 38–42; Echevarria Alonso, La actividad
comercial, 40–48 and 92. Supplement 5.1.2 offers more governmental worries
about overfishing.
53
Susłowska and Urbanowicz, “Szczątki kostne ryb,” 53–65. Early medieval remains of fish
distinctly larger than later norms for the same species are also remarked by Kozikowska,
“Ryby w pokarmie średniowiecznych (X–XIV w.) mieszkańców Wrocławia,” 3–14; Paul,
“Knochenfunde,” 59–60; and Driesch, “Fischreste aus Hitzacker,” 420–421.
54
Clavel, L’Animal, 146–149: European flounder and plaice are not easily distinguished
archaeologically, for they share many skeletal elements and the same benthic habitat. At
Abbeville especially the largest specimens (over 45 cm) had vanished by 1300, became
fairly common again around 1400, and were disappearing by 1500. The average size of
plaice landed by Dutch coastal fishers also began to fall from the fifteenth century (Dam,
“Feestvissen en vastenvissen,” 491–492).

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 196 The Catch

Sturgeon in fish remains from 10th to 14th century Gdańsk

100%

90%

80%
percentage of fish remains

70%

60%

50%

40%

30%

20%

10%

0%
10th 11th 12th 13th 14th18th

Figure 5.1 Sturgeon in fish remains from tenth–fourteenth-

century Gdańsk. Data as published in Makowiecki, “Exploitation,”
fig. 7, and “Usefulness,” fig. 3, p. 109. Graph © R. Hoffmann.

banquets, even well away from the sea.55 As salmonid remains preserve
poorly in archaeological contexts56 it is worth observing the presence of
salmon bones in excavations from Anglo-Saxon Wraysbury in Berkshire,
the local Slavic prince’s dwelling at high medieval Hitzacker on the Elbe,
twelfth-century castles along the lower Rhine, the neighbourhood of the
late medieval Louvre palace, and a contemporary house of canons at
Saarbrucken.57

55
Association of salmon with “the very proud and rich” in the Cluny customal was
remarked in Chapter 2 above (Bruce, Silence and Sign Language, 177). Some other
systems used the same sign for sturgeon. See further, for example: Anthimus De
observatione ciborum, ed. Lichtenhan, pp. 18–20, or tr. Grant, §41 (pp. 66–67); Jacques
de Vitry, Exempla, ed. Greven, p. 26; Dyer, “Household accounts,” 116; Serjeantson
and Woolgar, “Fish consumption,” 104 and 124; Serrano Larráyoz, La mesa del rey,
200–203; Piekosiński and Szujski, Najstarsze księgi, 271–286 passim; Santucci,
“Nourritures et symbols.”
56
Heinrich and Heidermanns, “Lachs.”
57
Coy, “Fish bones,” 118; Driesch, “Fischreste,” 401; Reichstein, Untersuchungen an
Tierknochen von der Isenburg; Desse and Desse-Berset, “Pêches locales, côtières ou
lointaines”; Huster-Plogmann, “Fische.”

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 5 Aquatic Systems under Stress, c. 1000–1350 197

By the 1200s good anecdotal and other evidence across much of

western Europe indicates decline of natural salmon stocks in especially
smaller rivers and upper tributaries. Contemporaries attributed the
depletion to barriers and competitive overfishing, but habitat changes
resulting from agricultural clearances are also implicated. Historian
Angelika Lampen traced the collapse of salmon in archives of the convent
at Werden on the Ruhr from abundance in the eleventh century to
absence in the fourteenth.58 Fears of damaged salmon runs were voiced
in mid-thirteenth-century Northumbria and complaints of weirs and
illegal fishing killing smolts and damaging runs could soon be heard on
the Thames, Severn, Wye, and Meuse.59. On the small coastal rivers of
lower Normandy, where plowed fields and watermills multiplied through
the twelfth and thirteenth centuries, the generous annual gifts of salmon
offered in eleventh- and twelfth-century charters from reliable local
catches were distinctly fewer by 1300. Continued ‘overfishing’ thereafter
brought near-total destruction of the runs by the mid-1400s, with local
records referring rather to gifts of individual salmon imported from
Ireland and Scotland.60 From the fifteenth-century start of suitable
records along the middle Rhine the numbers and weights of salmon there
taken go steadily downwards.61 Many river basins saw by the later
Middle Ages the pressure on salmon shift down to estuaries, making it
out to be a marine rather than inland fish.62 Even in wealthy Parisian
households and prosperous Flemish monasteries consumption of once-
favoured sturgeon, salmon, trout, and whitefish shrank to undetectable

58
Lampen, Fischerei und Fischhandel, 208.
59
Page, ed., Three Early Assize Rolls, 103; London TNA, Plea Rolls: KB 27/509 11R2,
m1d; Wright, Sources, 91; Williams, Welsh Cistercians, 75–76; Kowaleski, “Seasonality,”
132–133. The second statute of Westminster (1285) ordered protection of smolts. Mid-
fourteenth-century financial accounts kept for the Counts of Namur indicate the collapse
of a functional salmon fishery in middle reaches of the Meuse (Balon, “La pêche,”
28–31).
60
Halard, “Peche du saumon,” 175–177. On the best-known river, catches in 1423 were
less than a third those of the early 1300s, though the price per fish rose by a factor of
twelve. Less grain-centred agrarian regimes and rivers unsuited to be spanned by mill
dams help explain strong survival of Irish and Scottish salmon stocks (Hoffmann, “Salmo
salar in late medieval Scotland,” 64–65).
61
Volk, Wirtschaft und Gesellschaft, 350–367. Lenders et al., “Historical rise of
waterpower,” would generalize this medieval decline across the entire lower
Rhine catchment.
62
As seen in Laurière et al., Ordonnances des roys, vol. 2 (1729), 578–582; Puñal-
Fernandez, Mercado en Madrid, 169–175; Martens, Mittelalterlichen Gartensiedlungen,
154–156; Benecke, “Beiträge,” 308–309 and 314–315; Sarnowsky, Wirtschaftsführung
des Deutschen Ordens, 130–131; Martens, De zalmvissers van de Biesbosch, 41–54,
114–135, and 211–219.

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 198 The Catch

by around 1500.63 Yet despite general late medieval increase in consump-

tion of marine fishes, salmon retained high cultural significance and com-
mensurate prices across their entire northern and western European range.
Like the sturgeon, then, Salmo salar is a prime example of widespread
localized medieval human impacts on European riverine, notably anad-
romous, fish populations. European fishers and consumers were well
aware of these losses long before modern industrialization.

5.2 Beneficiaries?
A schedule of tolls taken around 1275 by seigneurs of Audenarde
(Oudenaarde) at their bridge over the Scheldt en route to Ghent speci-
fied only four fish taxa: salmon and sturgeon paid per specimen, two and
four denier respectively; eel and herring turned over a hundred fish per
los (“Last”), a measure of quantity, probably 12,000, so weighing about a
metric ton.64 Different fiscal assessments reflect some of the previous two
or three centuries of change in the status of fish stocks and consumption
demand, contrasting the traditional elite favourites from threatened
anadromous species with smaller more numerous varieties, possibly
more resilient, for a broader range of consumers. Variant critical adapta-
tions and regional ecologies across western Christendom help explain
especially large increases since around 1000 CE in consumption of eel
and herring, and also the territorial spread of common carp, three fishes
and fisheries then on trajectories opposite to those of salmon and stur-
geon. In subtle ways all had gained from socio-economic developments
typical of high medieval Europe.

5.2.1 Eel
Eel are as migratory as salmon but travel in reverse directions
(catadromy). Unlike the sensitive eggs and young of salmon, subadult
eels enjoy broad ecological tolerances and omnivorous habits during
their long maturation in estuaries and waters far inland. With well-
chosen techniques people could catch eels throughout their freshwater
phase and when the sexually mature adults migrated downstream to
spawn at sea. Despite cultural antipathies to its snake-like morphology

63
Desse and Desse-Berset, “Pêches locales, côtières ou lointaines,” 125–126; Sternberg,
“L’approvisionnement de Paris en poisson”; Ervynck and Van Neer, “De
voodselvoorziening,” 425–426.
64
Verriest, ed., Le polyptyque illustré, fol. 12r. Unless specific sources indicate otherwise, the
last as a quantity (rather than a volume) counted ten “long thousands” of 1,200
items each.

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 5 Aquatic Systems under Stress, c. 1000–1350 199

and benthic habits,65 this species evidently supported long-standing

fisheries and human consumption in Atlantic and Mediterranean (but
not Danubian or other Black Sea) drainages. Until sieving became
standard archaeological practice, tiny bones and high oil content made
eel remains evasive, but regular fishing of eel at weirs, mills, and in
stillwater habitats everywhere supported heavy local consumption of
fresh and lightly processed catches throughout the earlier Middle Ages.
Human activities described to start this chapter greatly enlarged
nutrient-rich stillwater habitats, with the unplanned result of much
favouring the eel and soon those who could fish for it. In precociously
deforested England as early as the seventh- through mid-ninth centuries,
eel was the most common taxon in all fish remains recovered from
multiple contexts at York and in elite settlements at Canterbury and
Lyminge, Kent. In decades around 1000 it remained as abundant at
York, though yielding primacy to herring, and there continued in that
second rank until the 1200s.66 Further inland in Aelfric of Eynsham’s
time (c. 1000) eel were the single most common fish eaten in his monas-
tery and from the twelfth century there, too, remained second only to
preserved herring.67
Contemporary fish remains from northern France and the Low
Countries point to parallel developments. Eel reached two-thirds of
remains from twelfth-century Deventer, but thereafter fell back to only
one-third behind undifferentiated small cyprinids.68 In the Somme basin
eel emerge as the most common fish species from the ninth century with
special abundance in urban contexts at Amiens through the twelfth and
thirteenth. Although herring later steadily gained pre-eminence there,
even as late as 1449 Cistercians at Gard abbey on the Somme were

65
See views transmitted by Anthimus, De Observatione Ciborum (Lichetenhan, ed, p. 19:
Grant tr., p. 65); Hildegard of Bingen, Physica, lib. 5, §33 (Hildebrandt and Gloning,
eds., vol. 1, pp. 283–284); Albertus, De Animalibus, lib. 24, §3; and legends of a saintly
bishop expelling eels from Lake Lausanne (Chène, “Une sainteté exemplaire”).
66
Harland et al., “Fishing and fish trade,” 174–186, and Reynolds, “Social complexities,”
215–218. Dietary primacy at St. Augustine’s abbey, Canterbury, shifted from eel to
herring at about the same time as York (Nicholson, “Fish remains”). While eel remains
at Lyminge outnumbered those of herring by ten to one, in the contemporary coastal site
of Bishopstone on the east Sussex coast, eel provided only 20% of remains and herring
26%. Orton et al., “Catch per unit research effort,” 15 and fig. 9, find a high medieval
rise of eel consumption in London.
67
Hardy et al., Ælfric’s Abbey, 356–359 and 395–396. Also at Wraysbury on the Thames,
eel comprised 82% of fish remains from the late ninth century through early twelfth
(Coy, “Fish bones”). Holmes, Animals, 51–53, table 3.3, found eel at the largest share of
Late Saxon and Saxo-Norman sites with fish remains.
68
Clavel, L’animal, 101–102; IJzereef and Laarman, “Animal remains from Deventer,”
435–436.

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 200 The Catch

handling in single transactions as many as 13,000 eel. In food waste

which fell through gaps in the kitchen floor in the contemporary
Benedictine abbey at Ename outside Oudenaarde, eel remains at 12.6
percent of all fish (and 20 percent of those locally acquired) were also
outnumbered only by herring.69 Much further south in kitchen waste
from the priory at Charité-sur-Loire eel ranked second only to small
native cyprinids from the eleventh century to the sixteenth, when those
monks turned to carp as the main fish on their menus.70
Across the whole Rhine delta region of Holland and Flanders, a great
and long-term expansion of shallow estuarine and freshwater lakes since
at latest the 1200s resulted from subsidence of drained peat lands, peat
mining, diversion of rivers, rising water levels, and both local- and large-
scale wave action. These turbid, fertile, and accessible lentic habitats
soon supported large and lucrative commercial fisheries for eel. Sluices
of the Spaarendam beside Haarlem in the late 1400s annually yielded
150,000 eel (ten to twenty tonne). Fishers supplied towns in the region
and even exported to England.71 Where anthropogenic environmental
change came later than it had further west, as in Poland, eel populations
and human use of this fish may only more slowly have expanded
inland.72
Western Mediterranean watersheds show similar trends. In the Rhône
delta eel replaced sturgeon as the principal fishery by the fourteenth
century, but already in the twelfth residents were alert to the lucrative
returns possible from active fishing and storage of live eel in enclosed
ponds or channels.73 Energetic Italian pursuit of this species got under
way then, too. Local eel fisheries spread along Tyrrhenian shorelines
from Tuscany to Sicily, into the Adriatic around the mouths of the Po,
and in natural lakes and marshy river valleys of the interior, all locations
where other kinds of evidence indicate increased lagoon formation,

69
Clavel and Cloquier, “Pratiques halieutiques fluviales,” 207–208; Cloquier, “Pêches et
pêcheries”; Ervynck and van Neer, “De voodselvoorziening,” table 2 and p. 430
(although in the latter case remains of indeterminate cyprinids and flatfishes were both
still more numerous).
70
Audoin-Rouzeau, Ossements animaux, 147. For more French eel consumption see
Supplement 5.2.1.
71
Dam, Vissen in veenmeren, 103–121, and “Eel fishing in Holland”; Van Neer and
Ervynck, “Apport de la archéologie.”
72
Makowiecki, Historia, 145. Dembińska, Konsumpcja żywnościowa, 52, observes rising
verbal references to eel from twelfth–fourteenth-century northern Poland (Pomerania),
but the archaeological record is sparse.
73
Stouff, Ravitaillement, 201–203; Amargier, “La pêche en Petite Camargue,” 331–336;
Weiss, Versorgung des päpstlichen Hofes, 394–397; Berman, “Reeling in the eels.”

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 5 Aquatic Systems under Stress, c. 1000–1350 201

siltation, and eutrophication.74 So great was demand that from at latest

1275 each autumn the commune of Perugia sponsored transfers of
juvenile eel (elvers) from the Chiana river into Lake Trasimeno and
continued to do so even after Pope Martin IV died there in 1285 after
eating [too many?] eel. During the 1350s and 60s the papal-owned
fishery at the outlet of Lake Bolsena continued to ship thousands of eel
a year to the curia then in Avignon.75 Eel matched sea breams as the most
common fish taxa eaten at a late fourteenth-century palace in Tarquinia,
just up the coast from Rome.76 We can but speculate on the point of
balance for medieval eel stocks between anthropogenic enlarged habitats
and intensified human predation.

5.2.2 Herring Fisheries on the Rise

People fishing for and eating herring enter the historical record of
Atlantic (including North Sea and Baltic) coastal communities during
the early Middle Ages.77 Then with simultaneous rising human numbers
and environmental pressures of the tenth through thirteenth centuries
these activities greatly increased in scale and distribution into nearby
inland districts. Herring bones are as fragile and elusive in unsieved
archaeological contexts as are those of eel. (Figure 5.2) Though pelagic
in habits, schools of these plankton eaters once frequented close inshore
waters off northwestern European beaches and penetrated deeply into
now long-obliterated estuaries there.
From the south coast of the Baltic all the way around to the English
Channel seasonal spawning concentrations offered local opportunities
for rich catches within sight of land.78 Reproductively isolated estuarine
stocks could be taken in fixed traps and weirs and those along open
shorelines from small boats with light seines and drift nets, especially at

74
Compare, for instance, Grove and Rackham, Nature of Mediterranean Europe, 290–311;
Bresc, “La pêche … dans la Sicile,” 167–169, Un monde méditerranéen, 261; and “La
pêche dans l’espace normand,” 280–282; Vendittelli, “La pesca nelle acque interne,”
116–123, and “Diritti ed impianti,” 409–422; Lanconelli, “Gli Statuta pescivendulorum
urbis,” 94–102; Vincenti, “La tutela ambientale”; Rombai, “Le acque interne in
Toscana,” 30–42; Spicciani, “Il Padule di Fucecchio,” 64; Balletto, Genova nel
duecento, 189–192; Onori, L’abbazia di San Salvatore, 55–56; and Martin, “Citta’ e
campagna,” 333–334.
75
Lanconelli, “I lavori alla peschiera”; Biganti, “La pesca nel lago Trasimeno,” 795–797.
76
Clark et al., “Food refuse … Tarquinia,” 240–242.
77
For more context on herring history and historiography see Supplement 5.2.2.
78
For relevant biology see Fish Base, sub Clupea harengus; Hodgson, The Herring, 15–24;
Klinkhardt, Der Hering; Bailey and Steele, “North Sea herring”; Krovnin and Rodionov,
“Atlanto-Scandian herring,” with a useful summary from a historical Anglocentric
perspective in Locker, Role of Stored Fish, 31–44.

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 202 The Catch

Figure 5.2 Archaeological herring bones, unsorted. Herring and other

bones from the Blue Bridge Lane site, York, fourteenth century.
Photograph © James Barrett. Used with permission.

night. Writing about 1200, Danish chronicler Saxo bragged that the fish
along the Scanian coast were so abundant that they blocked shipping and
could be caught by hand.79 But these oily creatures spoil in a day unless
promptly dusted with salt, smoked, or packed in simple salt brine. Such
light cures make herring – ‘powdered,’ ‘red,’ or ‘pickled’ – an inexpensive
portable food, palatable enough for several months, especially during the
cold season after the autumn spawning. By the mid-twelfth century
coastal artisans from Picardy to Pomerania were tapping the silvery
billions to feed themselves, their neighbours, and nearby inland popula-
tions, especially in fast-growing towns.
The booming twelfth-century herring industry had emerged from a
historically obscure century and more of parallel development by fishers
with access to local consumers and local fish. Early medieval coast-
dwellers from Sussex to Sweden ate herring they, their neighbours, or

79
Saxo, Gesta danorum, preface 2:4 (Olrik and Ræder, ed., vol. 1, p. 6):
Ab huius ortivo latere occasivum Scaniae media pelagi dissicit interruptio, opimam praedae
magnitudinem quotannis piscantium retibus adigere soliti. Tanta siquidem sinus omnis piscium
frequentia repleri consuevit, ut interdum impacta navigia vix remigii conamen eripiat nec iam
praeda artis instrumento, sed simplici manus officio capiatur.
Also tr. Fisher, History of the Danes, vol. 1, p. 7. Albert, De animalibus, 24:2, observed
the abundance of these tasty little fish in waters off France, Britain, Germany, and
Denmark (“allec piscis est maximae multitudinis in Occeano quod partes Galliae et Angliae
et Teutoniae et Daciae attingit”).

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 5 Aquatic Systems under Stress, c. 1000–1350 203

their subjects caught from local shoreline and estuarine stocks.80 By

about 1000 these catches were also supplying nearby inland con-
sumers.81 At Haithabu on the Schleswig isthmus, where Viking traders
gathered from about 800 until 1066, this species contributed 38 percent
of the 13,842 identified fish bones. The oldest medieval herring remains
in inland Flanders appear only in the late tenth/early eleventh century
and those only in the mercantile settlements at Ghent and Ename.82
Until this time herring everywhere looked like a traditional subsistence or
artisanal fishery being practiced seasonally along seashores close
to consumers.
The eleventh century was then plainly transitional at many places
around the herring coasts, with remains of that species at York,
London, and elsewhere in eastern England a principal marker for archae-
ozoologist James Barrett’s ‘Fish Event Horizon,’ the significant appear-
ance of marine fishes in local diets.83 Some of the first strong evidence of
heavy commercial use comes from the Pomeranian coast of the Baltic
and southern shores of the North Sea. Before 1100 inland Poles were
well aware that the beaches between the Odra and Wisła estuaries were
full of fresh herrings and a source for salted ones. The rich representation
of herring in food remains from coastal sites thins out toward the interior.
Still, from Pomerania likely came the herring bones found in some
strongholds of the emergent Polish state along the Warta c. 1000 and
more commonly in eleventh–twelfth-century layers there and even so far
inland as Wrocław. By about 1200 Silesian nuns were sending small
boats down the Odra to pick up “salt fish.”84 An intensified fishery off

80
Kowaleski, “Early documentary evidence,” 23–24; Loveluck, Northwest Europe, 198–200
and 211; Reynolds, “Social complexities”; Enghoff, “Herring and cod,” 137; Barré,
“Droit maritime médiéval,” 524–525; Makowiecki et al., “Cod and herring,” 118–119;
and in many of the references to follow.
81
But not meaningfully earlier. For credible indicators of the absence of herring-eating
inland, see Supplement 5.2.2.
82
Van Neer and Ervynck, “Rise of sea-fish consumption,” 159–164; Enghoff, “Baltic
region,” 48, 56–58, et passim; Enghoff, “Denmark,” 177 and 142–143; Lepiksaar and
Heinrich, Fischresten aus Haithabu, 119; Heinrich, “Temporal changes,”151–156. As
Locker (Role of Stored Fish, 114–168) argues, when archaeologists have carefully sieved,
individual herring are so small that their share of fish flesh consumed was much less than
their proportion of all bones recovered.
83
Barrett et al., “Dark Age economics” and Barrett et al., “Origins of intensive marine
fishing,” more fully shown in Orton et al., “Fish for the city,” 517, and Harland et al.,
“Medieval York,” 175–193. For herring at least this was a more widespread, if plainly
incremental, phenomenon.
84
Leciejewicz, “Z denara” and “Zum frühmittelalterlichen Heringshandel”; Rulewicz,
Rybołówstwo Gdańska, 68–88 and 342–347; Makowiecki, “About the history of
fishing,” 120; Makowiecki, “Catalogue”; Makowiecki et al., “Cod and herring,”
118–123; Chełkowski and Filipiak, “Cognitive potential,” 45; Kozikowska, “Ryby”;

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 204 The Catch

the island of Rügen, however, seems a twelfth-century development,

soon contested between Slavic and Danish lords.85
Parallel developments along continental coasts of the North Sea and
Channel from Flanders to Normandy are signaled in cartloads of herring
on the market at Arras in 1024, an annual herring fair at Fecamp by
1088, and herring remains at eleventh-century sites as far inland as
Compiègne, Paris, and Namur, though in the latter only at the castle,
not yet the less affluent town. By the second half of the twelfth century
communities along the Flemish coast had gained a papal dispensation to
fish on Sundays while the run was on, and were struggling bitterly with
old neighbouring monasteries over payment of tithes on their catch,
which assumed a large presence on their newly established fish markets.
The material results of these efforts are plain in abundant herring bones
found in twelfth- and thirteenth-century urban contexts (see Figure 2.2
above).86
Across the narrow seas historian Maryanne Kowaleski estimates a
four-fold increase in English herring catches from c. 1000 to c. 1200.
Domesday Book (1085–1087) counted well over a score of large site-
specific renders in herrings owed the king and East Anglian lords. This
argues for a widespread fishery, if seasonal and by part-timers, and
accounts for the newly high proportion of herring remains in food waste
from twelfth-century Norwich, London, and other locations in eastern
England. Transport some distance inland is revealed by mentions of
herring in toll schedules.87 Exploitation also of local herring stocks in

Lampen, Fischerei und Fischhandel, 168–171; Gallus, “Chronicon Poloniae,” lib. 2,

cap. 28; Herbord, Dialogus de vita S. Ottonis, lib. 2, c. 41 (Liman and Wikarjak, ed.,
p. 141); Appelt and Irgang, SUB, #123 and 140. Writing around 1120, chronicler
Cosmas of Prague described Bishop Gebhard of Prague in 1090 distributing Lenten
herring to the poor (Chronica bohemorum, 2:42, ed. Bretholz, p. 147).
85
Jahnke, Silber des Meeres, 15–38; Lampen, Fischerei und Fischhandel, 163–168.
86
Van Drival, ed., Cartulaire de Saint-Vaast, 166; Hocquet, “Pêcheries médiévales,” 39–49
and 79–86; Darsel, “Le servitudes,” 107 (eleventh-century Dieppe paying dues in
herring to St. Catherine’s of Rouen); Clavel, L’Animal, 161; Pigière et al., “Status as
reflected in food refuse,” 238–241; Kapferer, Fracas et murmures, 93–96; Coopland,
Abbey of St. Bertin, 47–48; Derville and Vion, Histoire de Calais, 14–15; Uytven,
“L’approvisionnement des villes,” 102; Van Neer and Ervynck, “Inland Flanders,”
p. 164, fig. 14.5. Fiscal evidence of the twelfth-century Flemish fishery is in
Delatouche, “‘Gros Brief’ de Flandre,” 30, but the count of Boulogne had already
before mid-century donated to Cluny from his own royalties 20,000 herrings a year
(Bernard and Bruel, eds., Recueil des chartes, #4132, p. 481).
87
Kowaleski, “Early documentary evidence,” 23–31, and “Commercialization,” 178–180;
Locker, “Peabody Site”; Locker, Fishergate, Norwich, 42–44; Locker, Role of Stored Fish,
170–191 and 277; Riddler and Trzaska-Nartowski, “From Dover to New Romney”;
Lovelock, Northwest Europe, 251–252 and 353. Campbell, “Domesday herring,” thinks
Domesday accounts for only 5% of the English catch, which would then come to more
than three million fish or three hundred tonnes.

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 5 Aquatic Systems under Stress, c. 1000–1350 205

southwestern England sustained payments of 30,000 herring a year from

Tidenham (where the Wye enters the Severn estuary) to the minster of
Bath. When herring came to 60 percent of the fish bones gnawed by the
monks of Norman Eynsham, did those rations come from the Severn or
the North Sea?88
Most everywhere at this time the greater share of this catch was piled
up whole right on the foreshore and covered with salt, making loose dry
‘powdered’ (sapoudre) herring with a few months’ storage life, then sold
in bundles or baskets of a thousand to consumers as much as a hundred
kilometers away.89 Already in the 1160s Alan of Lille called herring “the
most common of fish, [which] by his wide availability relieved the hunger
of the poor.”90 Plainly the surging exploitation of abundant herring
stocks along Christendom’s northwestern littoral during the eleventh
and twelfth centuries contributed heavily to increased quantities of
marine fishes serving to meet the growing demand for fish as food in
maritime Europe.
At least into the 1200s, however, written and archaeozoological
records known to date indicate that consumption of herring remained
an essentially regional phenomenon which rapidly attenuated towards
the continental interior. Even in the twelfth century herring bones in
Parisian trash still number but two-thirds those of eel. Further inland
eleventh- and twelfth-century written evidence is confined to ecclesias-
tical settings while material finds are absent even from well-sieved sites.91
In the eleventh-century Rhine basin monastic writers at Lorsch and St.
Gallen describe the fish in learned terms referring to Roman fish pickle,
not dry salted objects, and the only physical traces come from a castle
near Basel. By the mid-1100s verbal acquaintance among monks at
Hirsau and of Hildegard of Bingen with the preserved product gains

88
Lovelock, Northwest Europe, 207; Hardy et al., Aelfric’s Abbey, 379–381. Fishing for
nearshore migratory herring schools in the Firth of Forth is documented in the twelfth
century, supported by salteries in the immediate area (Oram, “Estuarine environments,”
366–367).
89
Harland et al., “Fishing and fish trade,” 189–190, makes clear that the herring consumed
at eleventh–early fourteenth-century York had not been processed for packaging in
barrels, so had to be consumed fresh or shipped dry-salted. Those reaching Bourges
about 1100 by way of boats on the Loire paid toll by count (Querrien, “Pêche et
consummation,” 428–429) and so did the herring entering Flanders as late as 1252
(Lampen, Fischerei und Fischhandel, 186, citing Hansische Urkundenbuch, vol. 1, no. 432).
90
Alanus, De planctu, Prose 1, tr. Sheridan, 94–98.
91
Clavel, L’Animal, 154–160; Jarecki, Signa Loquendi, 122–124 (Ulrich of Cluny) and
252–253 (Fleury); Bernard and Bruel, eds., Recueil des chartes, #4132, p. 481;
Sternberg, “Une spécificité de la cuisine monastique,” 93–94, points out absence of all
marine fish from abundant sieved kitchen remains at eleventh–thirteenth-century
Tournus on the Saône and at La Charité-sur-Loire.

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 206 The Catch

but tepid confirmation from rare finds in slightly later urban latrines at
Basel.92 In Bavaria no herring bones are reported in a survey of fish
remains from six castles and four urban contexts predating 120093 nor
do they leave any trace in either the Iberian or Italian peninsulas. Further
east in the Baltic than Viking-Age Birka in Sweden, herring likewise
occur only after 1200.94
Expanding eel fisheries at (western) European scale met growing
medieval demand for fish by exploiting a species whose habitat itself
was then growing in unintended consequence of human activities.
Herring, however, epitomize intensified human use in northwestern
coastal areas of an existing fish stock under conditions where larger
cultural and demographic demand pressures confronted limited and
probably dwindling supply from hitherto preferred varieties taken in fresh
water. In a third emerging case during the same tenth through thirteenth
centuries, the westward spread and human use of common carp repli-
cated some features of the two previous, but reached across the extensive
upper Danube basin into neighbouring waters then little affected by
intensified consumption of eel or herring.

5.2.3 Exotic Carp Invade the West

The tale of carp in central medieval times relates the progress of what
would now be called an exotic and invasive species. Throughout Greco-
Roman antiquity common carp resided in European waters only in the
Black Sea drainage, where remains from some Balkan sites suggest it was
abundant. The northwesternmost traces of this fish up to and throughout
the Roman Empire placed it in the Vienna basin, the most westerly part
of Pannonia.95 Not coincidentally, this natural post-Pleistocene range of

92
Ekkehard of St. Gallen, Benedictiones (ed. Egli, 285–289); Heinricus Laureshamensis,
Summarium Heinrici, lib III, c. xvi (pp. 156–160); Jarecki, ed., Signa loquendi, 165–168
(William of Hirsau); Hildegard, Physica, lib. 5, cap. 22 (Hildebrandt and Gloning, eds.,
vol. 1, pp. 278–279; tr. Throop, p. 71); Hüster-Plogmann, “… der Mensch lebt nicht
von Brot allein,” 193–197; Deschler-Erb et al., “Tierknochen aus St. Arnoul,” 529–532.
93
Pasda, Tierknochen als Spiegel, 106–110. Remains of other small-boned fishes
were recovered.
94
Lõugas, “Fishing and fish trade,” 111–112.
95
A systematic survey and interpretation of the material and verbal evidence summarized
in Map 5.1 is Hoffmann, “Remains and verbal evidence,” later slightly revised and
augmented in Hoffmann, “Environmental change and the culture of common carp.”
Subsequently Enghoff, “Fishing in the Baltic Region” and Enghoff, “Fishing in the
southern North Sea,” confirm these findings, both generally and in the discussion
pp. 100–107, as does Makowiecki, “Catalogue.” I remain unconvinced by single
isolated finds of alleged early carp bones found at waterside sites many hundreds of
years and kilometers away from other contemporary evidence and in regions where the

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 5 Aquatic Systems under Stress, c. 1000–1350 207

a slow-water, heat-loving but otherwise broadly tolerant, species ended

precisely where it encountered the fast-moving, high-gradient waters of
the upper Danube above that river’s ‘inland delta’ in the vicinity of
Bratislava. Contrary to assertions by some biologists, no written or
material evidence suggests that Romans dealt with carp outside that
native range or there handled carp any differently than they did other
freshwater fishes.96
In what remains the oldest known verbal European reference to this
organism, in the mid-530s Cassiodorus, the learned Roman minister for
the Gothic kings who ruled early sixth-century Italy, listed carpam destinet
Danubius (“the Danube sends carp”) among the several exotic fishes the
king would serve to impress visiting ambassadors.97 From Cassiodorus’
northern Italian standpoint, the pertinent Danube lay to the east in
Pannonia (modern Hungary or Serbia), whence the Goths had entered
Italy a generation before, where they then still also ruled, and where the
carp were not only native but long consumed by humans. Tellingly,
the only known material evidence of this fish from medieval Italy
is isolated fragments from sixth–seventh-century Comacchio and
Padua,98 precisely the time and route for such a luxury import to be
transported to the king’s palace.
During the half-millennium from Cassiodorus into the eleventh cen-
tury, finds of carp remains continue to confirm its natural distribution,
and for the first time indicate its spread (1) further up the Danube and
(2) north into middle reaches of the Odra and Elbe systems (Map 5.1).

fish is a well-known later introduction – as, for example, Dobney et al., Of Butchers and
Breeds, with a single purportedly third-century carp bone from Lincoln. More
confidence-inspiring recent evidence is mentioned below.
96
Balon, “The common carp,” 1–55. Indeed in this same region, the last remnant
population of wild, not feral, common carp, survived into the 1960s, when they were
so identified by the late biologist Eugene Balon. For the hydrological barrier see Balon
and Holčik, “Gabčíkovo river barrage system,” 2–4. As opposed to carp consumption in
the Roman Balkans, Balon’s assertions of Roman domestication of carp, as reiterated in
his Domestication; “Origin and domestication,” 21–32, and “About the oldest
domesticates,” 6–10, and set in the inland delta area or elsewhere, are in continued
absence of supportive material or written evidence to be construed as wishful thinking.
Carp remains at Roman and early medieval Austrian sites show a size distribution typical
of wild populations; only from the fifteenth century do carp of uniform size indicate a
farmed population (Galik et al., “Fish remains,” 349–350). For much of what follows,
Leonhardt, Der Karpfen, 12–15 and 49–54, embedded seminal ideas in much
historical error.
97
Cassiodorus, Variarum libri dvodecim, 12:4 (Fridh, ed., p. 467). Other fishes there meant
to impress visitors were to come from the Rhine, Sicily, and southernmost Italy. Carpa is
reputedly one of only two Gothic words Cassiodorus ever wrote (O’Donnell,
Cassiodorus, 94).
98
De Grossi Mazzarin, “I resti archeozoologici,” 56–57; Gabriel, “Fish assemblages,”
126–128.

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 208 The Catch

Map 5.1 The expanding range of common carp in Europe, 600–1600.

No verbal sources corroborate the northward expansion (presumably via

low divides at the headwaters of the Morava River), perhaps because
literate Latin Christian culture penetrated this zone only around
1000 CE and initially produced none of the requisite records of eco-
nomic activity. Carp’s early medieval westward push, however, did leave
traces in the eleventh-century written record. About 1060 the anonym-
ous author at Tegernsee abbey of a secular fairy tale (courtly novel),
composed in Latin, listed charpho together with other fishes, some named
in Latin, others in the vernacular but all otherwise familiar in upper
Bavaria, which his hero, a knight named Ruodlieb, captures by quasi-
magical means.99 Barely a generation later, Abbot William of Hirsau
(d.1091) compiled a vocabulary of signs for his monks to use during
compulsory silence. To his prototype from Burgundian Cluny, William
added several central European taxa, among them “the fish which is
popularly called carp” (piscis qui vulgari nomine carpho dicitur). Did
William then expect carp at Hirsau’s Black Forest site in the Rhine

99
Ruodlieb, Fragment X, ll. 36–48 (Haug and Vollmann eds., 2:1, pp. 136–137; Vollmann,
ed. and tr., pp. 494–495; Ford tr., p. 74). This identification is undisputed, as are most of
the other distinctively middle European/Danubian fishes in the list, but some of the
English names used in Ford, tr., p. 74, are entirely implausible.

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 5 Aquatic Systems under Stress, c. 1000–1350 209

basin, or did he recall eating this fish during his youth at Regensburg on
the Danube? Might William signify carp’s movement across water-
sheds?100 If so, this is corroborated by recent finds of carp remains from
tenth-/early eleventh-century layers at Sulzbach castle, seat of the Count
of Nordgau, in a zone of interlaced Danube and Rhine tributaries and
then, barely a decade after William’s death, by a bilingual lexicographer
at Lorsch abbey in the northern Black Forest who glossed a fish called in
Latin carabus with the German charpho.101 Carp remains of late eleventh-
and early twelfth-century date at Nürnberg castle and a house of canons
at Saarbrücken further fit this scenario.102
Five centuries from Bratislava to the Rhine; less than two from there to
Paris? Mention by Hildegard of Bingen in her Physica (c. 1160) confirms
the establishment of carp (carpo) in the middle Rhine. The abbess likely
learned from abbey fishers how the species fed on bottom organisms and
vegetation in swampy and clear water and something of its spawning
habits, while herself assessing its value as food and, suitably prepared, a
cure for fever.103 No remains or verbal mentions from before 1200 sug-
gest carp culture or artificial fishponds. These were wild fish.
Further west the written and archaeozoological records seem to lag,104
and then suddenly blossom in the mid-thirteenth century. Does this

100
Jarecki, Signa loquendi, 165–168. For William’s Bavarian background and subsequent
experience at Cluny, whence his model for the sign language, see Jakobs, Die Hirsauer,
8–30.
101
Pasda, “Tierhaltung als Spiegel,” 106–109, and “Tierknochen auf Sulzbach,” 254;
Heinricus, Summarium Heinrici, lib. III: cap. xvi (ed. Hildebrandt, 159–160). Latin
carabus was used by Pliny (Historia naturalis IX:LI) for a kind of crab, but in present-day
scientific nomenclature refers to a family of beetles.
102
Boessneck and von den Driesch-Karpf, “Tierknochenfunde Nürnberg,” 70–72;
Huster-Plogmann, “Fische,” 529–532, and Deschler-Erb et al., “Tierknochen aus St.
Arnoul,” 529–532, and personal correspondence with Heide Huster-Plogmann,
15 April 2014. Outer limits to carp’s range before the twelfth century are well
established. See Supplement 5.2.3.
103
Hildegard, Physica, lib. 5, cap. 5, cap. 11 (Hildebrandt and Gloning, eds., vol. 1,
pp. 273–274; Throop, tr., p. 168). More recent finds by Dutch and Swiss experts in
ichthyoarchaeology have better confirmed the presence of carp in the Rhine around
Hildegard’s time: twelfth- and early thirteenth–century remains from Utrecht are
independently attested in Buitenhuis and Brinkhuizen, “Faunaresten,” and
Beerenhout, “Het Huis te Vleuten,” while van Dijk and Beerenhout, “Het
botmateriaal,” 40–41, encountered carp bone at thirteenth-century Hoorn, on what
was then a still freshwater Zuider Zee. Closer to the top of the watershed the carp
remains from latrines in Schaffhausen suggested in Hüster-Plogmann and Rehazek,
“Historical record versus archaeological data,” to come from the twelfth century have
now been redated by the same scholars to the later Middle Ages (see Hoffmann “Der
Karpfen”).
104
Carp are conspicuously absent from late twelfth- and early thirteenth-century works by
writers associated with Parisian schools and evidently interested in fishes: Gui of
Bazoches, Epistolae 23 (Adolfsson, ed., pp. 89–99); Alexander Neckham, De naturis

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 210 The Catch

mark arrival or literate recognition? A Parisian connection seems import-

ant. All three preeminent mid-century scholastic natural philosophers
took cognizance of carp. Thomas of Cantimpre, who composed his Liber
de natura rerum during the early 1240s, associated the fish with ponds and
slow rivers. He had some idea of its morphology, fecundity, and ability to
evade the fishers’ nets, but was ill-informed of reproductive behaviour.
A decade or so later Vincent of Beauvais mostly replicated Thomas.
Thus when writing De animalibus in 1258–1262, Albertus Magnus could
select from and correct his predecessors. Perhaps drawing on his own
experiences in Regensburg and Köln, Albert revised errors about
spawning behaviour and commented on both the carp’s suitability for
rearing in artificial ponds and its culinary qualities (which Albert
doubted).105 Also in 1258 managers of the estate at Igny-le-Jard
belonging to Thibaut VI, Count of Champagne, “stocked 3520 carpis
and six big pike” costing more than eighty-three livres into one of their
ponds. Later that same year they spent still more to put into two ponds
some unidentified ‘fish’ (piscibus), 10,000 bream and roach (bremarum et
gardonum), and 400 carpis, the latter alone costing nineteen livres.106
Igny-le-Jard, still well endowed with ponds, sits midway between
Epernay and Chateau-Thierry, about three kilometers from the Marne
and less than a hundred upstream of Paris. Within the next decade royal
provost Etienne Boileau included carpes and cuerpiaus among the fishes of
the Seine and other fresh waters which artisan fishers and fishmongers
sold to Parisians.107 And from a mid-thirteenth-century rubbish pit
beside the castle of the Louvre come the oldest known carp remains in

rerum, lib. 2, c. 22–47 (Wright, ed., pp. 142–158); Bartolomeus Anglicus, De

proprietatibus rerum, lib. 13, cap. 26 (Frankfurt 1601 edition, pp. 578–587). Nor do
carp appear among the thirty-three fishes mustered for allegorical war in the French
“Battle of Lent and Carnival,” assembled in Picardy or Normandy at the start of the
thirteenth century (Lozinski, ed., La Bataille, 121, with dating 38–45).
105
Thomas of Cantimpre, Liber de natura rerum, lib. 7:22 (ed. Boese, pp. 258–259);
Vincent of Beauvais, Speculum naturale, lib. 17:40 (1624 edition, col. 1274); Albertus,
De animalibus, lib. 24:26 (ed. Stadler, pp. 1525–1526). Intellectual context is provided
by Hünemörder, “Die Geschichte der Fischbücher,” 188–193.
106
Longnon, ed., Documents, vol. III, 17–18. Another fragmentary account from 1285 had
thousands of carp going into ponds at the duke’s estates in the baillage of Chaumont
(ibid., p. 32).
107
Lespinasse and Bonnardot, eds., Métiers et corporations, titles 99–100, pp. 213 and 216.
The same rules also appear in a royal ordinance for marketing fish in Paris, which
Laurière et al., eds., Ordonnances, vol. 2: 583–586, give from a confirmation of 1320,
after (p. 575) expressing doubt about the 1254/8 date given that text by Delamare,
Traite de la Police, vol. 3: 298–302. Delamare had, however, access to manuscript
sources later lost (Bourlet, “L’Approvisionnement,” 6–7, and Auzary-Schmaltz, “Les
Contentieux,” 60). Philip IV’s 1289 fisheries ordinance set the value for carp at two per
denier (Duplés-Agier, “Ordonnances inédites,” 51).

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 5 Aquatic Systems under Stress, c. 1000–1350 211

France, followed in a human generation by the same from castles at

Laarne and Londerzeel in Flanders.108 The carp had made itself home
in Europe’s west-flowing watersheds.
How had this occurred? Not by entirely natural means, more as an
unintended consequence of human activities. Although scholastic nat-
ural historians and Parisian regulations of the mid-thirteenth century
treated carp as a wild fish, human agency with varying purposes in mind
had for the previous half-millennium meshed tidily with the tolerances
and tenacity of an aggressive organism to encourage its spread. As earlier
here discussed regarding eel, during the sixth–eleventh centuries and
later Europeans caught, prepared, and ate fish from their natural local
waters. This often entailed live storage of seasonal catches in tanks,
cages, or ponds close to such centers of consumption as elite residences,
castles, or monasteries. Charlemagne had mandated this practice for
royal estates in his capitulary De villis (c. 795), and other records suggest
such vivaria were reasonably common.109
Ensuing centuries witnessed increasingly purposeful construction of
individual ponds throughout western Christendom, some meant to keep
fish (vivaria, servatoriae, piscinae), others functioning as mill ponds or
moats but capable of holding fish, too. Lay seigneurs – as at eleventh-
century Lanzenkirchen castle in Lower Austria – may have led this
activity but churchmen like John of Metz, abbot of Gorze in Lorraine,
accepted lay gifts of ponds and built more themselves. Radiocarbon
dating to the period around 1000 of the oldest surviving artificial ponds
in Berri matches their entry into the written record and local acceleration
of woodland clearances.110 By around 1200 – so well before carp are
detected west of the Rhine – some ponds in Poitou, Maine, southern

108
Clavel, L’Animal, 133; Ervynck and Van Damme, “Archeozoölogisch onderzoek”; Van
Neer and Ervynck, Archeologie en Vis. Benoît, “La carpe,” provides an overview of
French records.
109
Boretius and Krause, eds., Capitularia Regum Francorum, #32, c. 21 and 65 (pp. 85 and
89). Exemplary such vivaria in lay and religious possession appear in the Carolingian
Brevium exempla (ibid., #128, pp. 250–256) and a mid-ninth-century survey of imperial
properties in what is now easternmost Switzerland and western Austria (Häberle and
Marti-Grädel, “Teichwirtschaft,” 150–151). Earlier structures were built at St. Denis
(“Chronique” 1987, 179–181) and documented in Burgundy (Bouchard, Flavigny, #3).
110
Galik, Private correspondence, “Fischresten aus … Lanzenkirchen”; Pertz, ed., “Vita
Iohannis,” 362; Pichot and Marguerie, “Sur l’aménagement,” 119–124. Elsewhere
across the territory where carp moved westwards see mills and ponds on estates in
lower Bavaria as described in eleventh–twelfth-century charters (Krausen, ed.,
Urkunden … Raitenhaslach, nos. 1, 2, 3, and 29), in Franconia (Cnopf, Entwicklung
der Teichwirtschaft, 10–12, and Mück, “Beginn der Teichwirtschaft”), and in Burgundy
(Bouchard, St-Marcel-lès-Chalon, #12).

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 212 The Catch

England, the Ile-de-France, Champagne, and Lorraine were equipped

with adjustable sluices and bypass channels to manage their drainage and
simplify mass harvest of fish.111 Even beyond the general effects of
woodland clearance, watermills, and localized eutrophication, long
before the carp arrived in the west, more or less unawares Europeans
were preparing just the kind of habitat this fish would enjoy.
Captured wild fish stocked early medieval store ponds, whether those
were isolated vivaria, run-of-the-river impoundments behind mill dams,
or had other primary purposes. Nothing indicates any purposeful choice
of variety or special care in storage; no document inventories these fishes
by name. The result was inadvertent selection for tolerance of captivity,
transport, and possible variations in water temperature, oxygen supply,
and food. Only tough and resilient species survived, even when moved
from one watershed to another, where a few escapees might colonize new
territory on their own. This practice long continued for single or even
multiple ponds where small wild fish were stocked for future growth, as is
first explicitly described on the Count of Champagne’s estate at Provins
in 1217–1219 (without naming the varieties) and in the 1230s in England
on the bishop of Winchester’s estates with bream, perch, roach, eel, and
pike.112 But just about that time French managers were beginning to put
juveniles of single named species into chosen ponds, as seen in the carp at
Igny-le-Jard.
Chapter 7 will explore implications of those ponds and carp domesti-
cation. For now the point is to acknowledge how synergies among rising
medieval demand for fresh fish, multi-purpose human management of
watercourses, and the resilient adaptability of carp jointly enabled that
species to colonize continental Europe’s western watersheds by the mid-
1200s.

5.3 Regional Manifestations of Changing Fisheries

Data presented in Table 5.1 from seven well-investigated local sets of
archaeological fish remains from the high Middle Ages encapsulate the

111
Generally for French ponds see Benoit and Wabont, “Mittelalterliche
Wasserversorgung,” 189–196; Gislain, “Le role des étangs,” 89; and Benoît and
Rouillard, “Medieval hydraulics,” 177–180. Local cases appear in Delatouche, “Le
poisson d’eau douce,” 174–175; Sanfaçon, Défrichements, 26 and 85–90; Blary, Le
domaine de Châalis, 31–40; Richard, “Le commerce du poisson,” 181–197; and
Grand and Delatouche, L’Agriculture, 544. See also Holt, “Medieval England’s water-
related technologies,” 65–66 and 83–88, and Aston, ed., Medieval Fish, passim.
112
Longnon, Documents, 3:1–7; Roberts, “Bishop of Winchester’s fishponds,” 130–135.
Belliard et al., “Increasing establishment of non-native fish species,” rightly consider
carp the first known invasive fish species in France.

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Table 5.1 Predominant fish taxa in large bone assemblages from selected high medieval sites

dated to number of Rank % Rank Rank Rank Rank Rank % Rank Rank Rank Rank All
identified Clupeids % % % % Eel Salmonids % Pike % % % other
fish remains Gadids Flat- Smelt Perch Cyprinids Carp taxa
fishes

York Coppergate 13th cent 1262 ❶ 54% ❷ ◌ ◌ 3 ◌ ◌ ◌ 7%

24% 15%
(includes
16%
haddock +
6% cod)

Paris Louvre 13th cent 2889 ❶ 38% ◌ 3% 3 ◌ ◌ ❷ ◌ 11%

Cour Carrée 5% 33%*

Charité-sur-Loire 11th-14th 1703 ◌ ❷ 3 ◌ ? ❶

kitchen/refectory century (freshwater
burbot
only)

Mechelen/Malines early 14th 161,464 ❶ 49% 3 8% 6% 9% ◌ ◌ ◌ ❷ ◌ 3%

Het Steen century extrapolated (35% herring 12%† 13%*
+ 14% indet.
from herring/sprat)
samples

Bremen Altmarkt late 13th 1255 ❶ ◌ 4% 3 ◌ ◌ ◌ ◌ ❷ 10%

century 41% 6% 39%

Lekno kitchen 1153-14th 830 3 14% ◌ ❷ 10% ❶ 2%

century 21% 53%

5 lowland Austrian mainly 1230 ◌ ◌ 10% ❷ ◌ ❶ 28% 3 7%

sites 13th (trout) 28% 27%
century

blank cell indicates taxon not found ◌ taxon present * includes a few carp † includes a few cod

Sources: York Coppergate: Harland et al., “Fishing and fish trade,” table 15.4, pp. 182–183, namely the column labeled 1200–
late 1200s, with proportions calculated by R. Hoffmann. When all Gadidae (haddock, cod, and other species) are totaled, they
come to 24%, so still not half of the herring. Flatfishes and pike (the leading resident freshwater taxon) trail at 3% and 2%.
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Table 5.1 (cont.)

Paris Louvre, Cour Carrée: Clavel, L’Animal, table IV, p. 13. The context was a trash-filled ditch beside the palace. While the
author calculated percentages on all bones, I have recalculated them based on identified remains, lumping the six carp bones with
the other cyprinids. In the remaining 11% of bones from Cour Carrée, no taxon or grouping exceeded 3%. No salmon or
sturgeon; gadids came to 2%, mostly whiting.
Charité-sur-Loire, monastic (Cluniac) priory kitchen and refectory: Audoin, Ossements animaux, 146–147, enumerates no
individual elements or taxa, though mentioning abundant bream among the cyprinids in early phases and barbel and ide in
the fourteenth century. Carp appear only from the fifteenth century and marine species are absent.
Mechelen/Malines, Het Steen: Troubleyn et al., “Consumption patterns … inside Het Steen,” tables 7–9, pp. 32–36. Context was
two very large cesspits in a structure then the municipal prison. Archaeologists agree that inmates at Het Steen represented a
cross-section of town society and ate mainly food supplied by their own households or purchased from outside.
Bremen Altmarkt: Galik and Küchelmann, “Fischreste,” 215–218, notably table 2, with proportions recalculated on base of the
identified bones. No carp are reported and only 1% each of eel and gadids. A smaller (104 identified bones) trash pit of similar
date nearby has a similar pattern, although the particulars had not yet been analyzed for ibid., 219.
Lekno monastic (Cistercian) kitchen: Makowiecki, Historia, Aneks 2, p. 188, item 203; Wywra and Makowiecki, “Fish in the
menu of Cistercians,” 65. Lekno is about 30 km south of Poznań. There are traces of sturgeon and catfish but few diadromous
species and no marine other than herring. Here listed are only the well-dated and sieved finds from the 2001 excavations, not
those earlier (item 202) at this site, which provide no additional taxa.
Five lowland Austrian sites, all located between Vienna and Linz: Galik et al., “Fish remains as a source,” table 1, pp. 344–345,
with composite calculations by R. Hoffmann. Sturgeon remains, mainly of beluga, came to 3%. Present were one bone each of
herring and a flatfish, with no sign of cods, mackerel, or any other marine organisms.
 5 Aquatic Systems under Stress, c. 1000–1350 215

conditions wrought after some centuries of human impacts and rising

social demand for fish pressing against traditionally desired natural local
and regional stocks. The focus here is now on the most numerous taxa:
regardless whether from fresh or salt water, in each case the four most
common varieties total more than 84 percent of identified remains. While
lamenting the absence of comparably rich reports from Mediterranean
Europe – would Spanish, Provençal, or Italian studies inform other con-
clusions? – inferences both ecological and economic must be drawn.
Behind quite significant local variations lay several common features.
By the thirteenth century people in all sites were eating fishes from
‘ecological guilds’ different than had their predecessors (see Chapter 3:
Section 3.1 and Supplement). The salmonids and sturgeons which lost
quantitative dietary importance needed two habitats, freshwater and
marine, and unimpeded access between them to sustain their anadro-
mous life cycles; their successful reproduction depended on relatively
cool, well-oxygenated, running water. In contrast the well-evidenced
(and easily recognized) remains of eel, small cyprinids, and carp lead
and stand for general increases in relatively more lentic and heat-tolerant
freshwater varieties. Cyprinids and pike, too, spawn by choice in weedy
shallows, and eel leave fresh water when ready to breed. Only at York, on
an oceanic island with relatively low diversity of cyprinids compared to
the continent, did that group not play a large role. Instead, any emerging
gap between traditional fish stocks and rising social demand was there
met from a more radical and nearby alternative, the inshore marine
environment producing pelagic herring. Large quantities of the silvery
plankton eaters also served consumers at Paris, Malines, Bremen, and
Lekno, while at greater distance from the sea herring lacked quantitative
significance at this time. Marine demersal codfishes (haddock in particu-
lar in the case of York, that and whiting at Malines) were, with the benefit
of historical hindsight, just arriving as a western European dietary option,
as likewise were carp at Paris and Malines – although long a staple in their
older Austrian range. Essentially, Europeans were eating more fishes
with broader environmental tolerances in place of traditional varieties
with narrower requirements.114

114
In Regier’s evocative terms (“Rehabilitation,” 93–96), sensitive ‘white fish’ were losing
habitat and yielding their prior importance in human catches and consumption to more
broadly tolerant guilds of ‘grey fish’ and ‘black fish’, whose favoured conditions were
less damaged and which, in certain regions and localities, were thus becoming more
common. Although in contrast to post-industrial impacts, preindustrial development
more affected lotic components of aquatic systems, the general ecological outcome was
closely similar as “through their greater flexibility [grey fish] come to dominate within
modified ecosystems.”

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 216 The Catch

Simultaneously much consumption had shifted down the trophic

pyramid. Most still-water cyprinids and carp in particular consume much
plant material, the small herbivorous invertebrates living on aquatic
plants, and various bottom-dwelling creatures (benthos); herring con-
sume mainly zooplankton, so eat only one step higher. Eel are more or
less omnivorous. The dietary importance of carnivorous pike and
salmonids had largely vanished from England and France but remained
significant in less densely developed Poland and Austria.115
Characteristic differences between the fishes which rose in importance
and those which fell thus argue for human impacts on medieval aquatic
ecosystems more complex than can be ascribed to overfishing alone.
Precisely the aquatic habitats needed by species under threat were the
ones being blocked or degraded by medieval agricultural, urban, and
industrial developments, which were, quite without human forethought,
raising the amounts of silt and nutrients in Europe’s watercourses and
the proportion of standing waters. But also, insofar as the fishes at risk
had long been favoured for human consumption, their largest and most
productive spawners, those best able to replenish the local stock, were
also the least likely to survive intensified fishing pressure.
Fishing is simultaneously an ecological and an economic activity.
From the latter perspective high medieval fishers responded to rising
human demand against limited traditional fish stocks by blends of inten-
sified and innovative work to exploit regional alternatives. Eel and to a
lesser extent herring were old local resources now put to ever greater use.
The former fishery took unconscious advantage of a likely anthropogenic
increase in stocks; the latter dipped more deeply and broadly into what
appeared to be unlimited marine abundance. In the Danube basin and

115
While early medieval Europeans likely consumed relatively more predatory freshwater
fishes (pike, pike-perch, trout) than did their heirs in 1200 or 1300, and eel, carp, and
small cyprinids are closer to the base of the freshwater food webs, evidence now
available shows no clear sign of a trophic cascade, where smaller, short-lived
organisms explode in numbers and biomass as a result of fishers selectively removing
large predators. Eel may have occupied and expanded a niche in part left available by
diminished sturgeon, whose possible earlier keystone role in large river and estuarine
ecosystems simply vanished. Was this a regime shift from one relatively stable ecosystem
to another? In contrast, the salmon actually participant in freshwater ecosystems are and
were not the adults, which do not feed in fresh water, but the young, which there
interact with other small salmonids and fishes of comparable size, habits, and habitats.
Unlike the Pacific salmons (Genus Oncorhyncus), Atlantic salmon adults do not in
temperate Europe transport in their dying bodies ocean-gathered nutrients essential
to life in infertile waters where their young must survive. European fresh waters are just
more nutrient-rich and diverse, even when the salmon are removed.

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 5 Aquatic Systems under Stress, c. 1000–1350 217

other inland areas neither eel nor herring could provide actual catches
nor then more than rare and occasional exotic food, so heavier use was
made of native cyprinids, perch, and some whitefishes, while some
people intervened more actively in the distribution and life cycle of carp.
Herring and to a lesser degree eel provided protein to a larger, less
wealthy, consumer base than had the traditional fisheries or the emerging
ones for carp or codfishes.
But for all the reasonable likelihood that forces and activities of medi-
eval Europeans both purposely and inadvertently drove significant alter-
ations to the subcontinents’s aquatic ecosystems and fish stocks, humans
were not the only probable post-millennial engines of change. The sparse
and lacunae-ridden record of the ninth through early fourteenth centur-
ies contains signs of naturally driven environmental fluctuations affecting
biodiversity and interactions among regional fish communities of interest
to human fishers and consumers.

5.4 Natural Dynamics

Although western Christendom as a whole enjoyed remarkably stable
climatic and seismic regimes during the central and high Middle Ages,
regional atmospheric and hydrographic conditions necessarily interacted
significantly with freshwater and marine aquatic ecosystems. In
what follows, a basic understanding of climate and hydrology will frame
how shifts in these natural parameters changed local land- and water-
scapes with likely consequences for fish populations and their use
by medieval societies. Again, shards of information long assumed irrele-
vant and disconnected form a mosaic when joined by known
ecological relationships.

5.4.1 Climatic and Hydrographic Fluctuations at Multiple Scales

Historical climatologists commonly describe the times treated in this
chapter in terms of the ‘Medieval Climate Anomaly’ (henceforth
MCA), a period in global climate history with patterns distinct from a
most recent reference period (roughly 1880s–1980s/2000 or shorter) and
from those of the intervening ‘Little Ice Age’ (henceforth LIA)
(Figure 5.3). At global scale the MCA entailed a slightly warmed planet
during the ninth through eleventh/twelfth centuries with peak tempera-
tures c. 800–1000 and gradual cooling thereafter, “albeit with important
differences regarding the timing and spatial extent” of these phenomena.
Twenty-first-century climate historians stress that global or hemispheric

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 218 The Catch

European Mean Summer Temperature Anomalies, 850-1550.

Variance from Mean Summer Temperature in 19611990
2

1.5

1
Medieval Climate Anomaly
L I t t l e I c e A g e
0.5

0.5

1

1.5

2
850 900 950 1000 1050 1100 1150 1200 1250 1300 1350 1400 1450 1500 1550
Year
Area-weighted June-July-August mean temperature anomalies relative to Europe means, 1961-1990, as reconstructed from nine annually
resolved tree-ring width (TRW), tree-ring maximum latewood density (MXD) and documentary records in Luterbacher et al., “European
Summer Temperatures.” Data set and permission from J. Luterbacher. Graphed for R. Hoffmann by K. Hoffmann

Figure 5.3 European mean summer temperature anomalies, 850–1550.

averages are less relevant than the regional conditions wherein humans
and other organisms experience the impact of climatic anomalies.116
Energy flowing from the sun (solar irradiance) and terrestrial volcan-
ism principally drove the earth’s premodern climate, with regional fea-
tures a result of global oceanic and atmospheric circulation.117 The
MCA coincided with high solar activity, especially during 1080–1280,
and flow of energy to the earth. Only one solar minimum during
1040–1080 (the Oort) took place during the MCA, which came to an
end with the Wolf minimum, 1280–1350. The ensuing LIA, a period of
cooler global climates, coincided with three more minima in rapid suc-
cession.118 Volcanic eruptions introduce aerosols and dust into the
atmosphere. These reduce arrival of solar energy to the Earth’s surface

116
Quotation from Diaz et al., “Medieval warm period redux,” 32. Christiansen and
Ljungqvist. “Northern Hemisphere temperature,” 277, confirm a greater geographic
variability during the MCA than the LIA. See also Glaser and Riemann, “Thousand-
year record of temperature,” 446; Luterbacher et al., “European summer
temperatures.” Discovery of this variability led climatologists to replace the term
‘medieval warm period’ with MCA and calls into question scientific or scholarly
explanations which assume unbroken or year-round heat at this time.
117
Steinhilber and Beer, “Solar activity.”
118
The Spörer minimum dated to 1460–1550, Maunder to 1645–1715, and Dalton to
1790–1820. For reconstruction across the MCA and LIA see Luterbacher et al,
“European summer temperatures,” as here replicated in Figure 5.3.

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 5 Aquatic Systems under Stress, c. 1000–1350 219

and often have a global or hemispheric cooling effect. After an intense

cluster of large eruptions and cooling during the sixth century, few
volcanoes affected the northern hemisphere until a series of eruptions
during the 1150s through 1260s, followed by another in the 1340s.
During much of the MCA global circulation patterns produced a positive
phase in the North Atlantic Oscillation (henceforth NAO), meaning
westerly flows from the Atlantic protected most of western Europe from
colder air out of Siberia. From 1100 to 1260 Europe’s average annual
temperatures surpassed twentieth-century norms. Growing seasons
remained at or above twentieth-century means from the mid-tenth cen-
tury through the 1250s, followed by a severe drop in the 1260s. That cool
spell dissipated after 1270 when temperatures rebounded for about
another human generation, followed, however, by great instability during
middle decades of the fourteenth century.119
Planetary or even large-scale regional average temperatures are only a
part, and not necessarily all that important a part, of how climate and
weather patterns affect living things.120 Fluctuations of hydroclimate
(precipitation and evaporation) do not necessarily coincide with tem-
perature in their timing nor the scale of variation. Specific regional
manifestations of both temperature and precipitation differ from the
large scale. Seasonal variations have the greatest impact at critical life-
cycle stages for both humans and fishes. Extreme events and other
environmental perturbations stress natural systems and societies depend-
ent upon them.121 So possible connections between climate and past
fisheries need to work at smaller scale.
Neither the writer and readers of this book nor their medieval prede-
cessors have direct physical perceptions of the abstraction ‘climate’ nor of
its changes. Without serial records and the patterns those may reveal,
humans experience meteorological events (weather), sometimes later
recall extremes (cold, storms, heat, drought), and may over time adjust

119
Goosse et al., “Origin of the European ‘Medieval Warm Period’,” 105–110; Trouet
et al. “Persistent positive North Atlantic Oscillation”; Seager and Burgman, “Medieval
hydroclimate revisited,” 11–12; Ortega et al., “Model-tested North Atlantic Oscillation
reconstruction”; and Franke et al., “North Atlantic circulation.” Christiansen and
Ljungqvist, “Northern Hemisphere temperature,” 765, conclude “The two-millennia
long reconstruction shows a well defined Medieval Warm Period, with a peak warming
c. 950–1050 AD reaching 0.6 C relative to the reference period 1880–1960 AD.”
European averages were probably higher, but still below those of the late
twentieth century.
120
Ljungqvist et al., “Northern Hemisphere hydroclimate variability.”
121
Campbell and Ludlow, “Climate, disease and society,” figure 1 and appendix 5,
construct for western Europe an “Index of Environmental Instability” to help
contextualize late medieval crises.

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 220 The Catch

their behaviour to patterned experience. When does the snow come?

How big a bridge will survive floods? When to expect the wheat harvest
or the bream to assemble in shallows to spawn? Catastrophic events can
transform habitats; gradual shifts in water temperature or chemistry can
have similar effect, though perceived by humans only as one kind of fish
replacing another. And over time human practices may change – though
not due to recognition of ‘climate change’.
If the intensely studied Tiber watershed in central Italy can stand for
conditions in western Mediterranean Christendom, after cooler than
average and increasingly wet weather from the fifth through the ninth
centuries, a warming trend set in and rose to a peak between the mid
eleventh century and mid twelfth only to cool again slowly into the
fourteenth. The region was distinctly drier between about 1050 and
1350 than before or after; the Tiber rarely reached flood stage.
Obstructed drainage, however, turned the valley floor around Rieti into
a permanent wetland of slow-moving waters.122 Surely the environment
for Carolingian-age fisheries of Farfa abbey (Chapter 3, pp. 101 and 107
above) had evolved. More general surveys of Italian conditions see
changing phases, with c. 1100–1270 typically warm and arid, while lake
core samples from eastern and coastal Spain give a similar impression.123
Subfossil remains of small vertebrate animals from sites along streams in
Corsica show different patterns of diversity during droughty high medi-
eval times than in subsequent wetter periods.124
North of the Alps the central European landscapes whence large rivers
flow into the North Sea, Baltic, and Danube, experienced a different
MCA. A period of peak temperatures was well defined in the mid-tenth
to mid-eleventh centuries, followed by decadal or longer cold spells after
1050, in the early 1100s, and again in the early 1200s. Increased season-
ality meant the thirteenth and early fourteenth centuries knew distinctly
warm summers but chilly winters.125 The positive NAO also produced
wetter summers, although tree ring data from both Scandinavia and the

122
Mensing et al., “2700 years of Mediterranean environmental change,” and Mensing
et al., “Human and climatically induced environmental change,” 54–57.
123
Seager and Burgman, “Medieval hydroclimate revisited,” 12; Ortolani and Pagliuca,
“Cyclical climatic–environmental changes”; Moreno et al., “Hydrological pattern.”
Written proxy sources (Camuffo and Bertolin, “Climate in the Mediterranean,”
figure 1, p. 127) indicate colder Italian winters set in about 1270 to 1360.
124
Vigne et al., “Sensibilité des microvertébrés.”
125
Glaser and Riemann, “Thousand-year record of temperature,” 444–447; Christiansen
and Ljungqvist, “Extra-tropical Northern Hemisphere temperature.”

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 5 Aquatic Systems under Stress, c. 1000–1350 221

Swiss Alps signals somewhat drier conditions in those boundary areas.126

Overall warmer summer waters might inhibit successful reproduction by
fishes intolerant of high temperatures while enabling successful spawning
by species preferring those conditions.
On maritime fringes off northwestern Europe the warming trend of the
MCA came early and may have reached its maximum sooner, too.
Greenland was at its warmest c. 800–1000, reaching 1.8 C above the
reference period. Norse settlers arrived at Iceland in 870 during a
hundred-year warm spell, suffered a chilly eleventh century, but then
between 1100 and the mid-1200s enjoyed the warmest summers in three
centuries. After 1280 cooling set in across all seasons. In northwestern
Scotland only a mid-eleventh-century drought interrupted otherwise wet
conditions from around 900 to 1340. Sea surface temperatures in the
North Atlantic – assessed from the barely visible fossil shells of
temperature-specific diatoms in bottom cores – fluctuated at the decade
scale through most of the twelfth century but then maintained high
values from 1170 to 1260. A hundred years of cooling followed.127
Put simply, around 1100, when Mediterranean Europe was close to its
warmest and aridity threatened some aquatic systems there, central
Europe was already cooling down, especially in winter time, but quite
well watered, and the North Atlantic coasts and islands, though very wet,
retained a moderated climate, though less warm than it had been some
centuries before. Organisms, ecosystems, and cultural adaptations at the
edge of their critical tolerances had the most to lose or to gain from
marginal changes.
Regional climate itself is but one component in the dynamic processes
visible at medieval Europe’s land–water interfaces, its marine estuaries,
coastal marshes, and open shorelines as well as the courses and banks of
its rivers. To begin at the headwaters, many preindustrial rivers took an
unstable local course. Seasonal patterns of flood, drought, and (in the
north) ice cover kept channels mobile and banks impermanent. During
high water rivers revisited their floodplains. Above the estuaries low
water commonly revealed braided structures – bars, islands, shallows,
multiple channels – as well as dominant constrictions, rapids, reefs, and

126
Seager and Burgmann, “Medieval hydroclimate revisited”; Amann et al., “Warm
season precipitation”; Büntgen et al., “2500 years of European climatic variability”;
Büntgen and Tegel, “European tree-ring data and the Medieval Climate Anomaly”;
McCarroll et al., “A 1200-year multiproxy record of tree growth and summer
temperature.”
127
Vinther, “Medieval climate anomaly in Greenland”; Campbell, Great Transition, 45–47
and 200–201; Cunningham et al., “Reconstructions of surface ocean conditions,”
929 and appendix 1.

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 222 The Catch

waterfalls.128 To the historic interplay of climate, topography, soils, and

human constructions rivers naturally responded with changes in morph-
ology and their associated aquatic habitats.
Distinct periods of frequent and large regional inundations associated
with short-term climatic instability occurred both during the MCA and
as it drew to an end. Rivers in English lowlands showed rapid seasonal
fluctuations and flood events during 1085–1117 and then again in the
thirteenth century, which triggered structural changes into multi-channel
forms.129 On the lower Rhine in the 1150s Emperor Frederick
Barbarossa instructed the bishop of Utrecht and counts of Gelders,
Kleve, and Holland to take measures to protect their subjects against
flooding. Two centuries later and further up the Rhine two religious
institutions went to canon law courts over changes to an island.130
Along both the upper Rhône and the rivers of the Pyrenees, after long
docile centuries, frequent and disastrous flooding set in from the end of
the twelfth century, rapidly increased through the thirteenth, and reached
a peak during the 1350s–60s.131 During that last wave of floods the upper
Rhône transformed from a meandering to a braided morphology,132
characterized by a higher gradient, coarser bed materials, large interann-
ual and seasonal variability, and thus newly unstable habitats for aquatic
life. Fluvial instability with human consequences even drew the mid-
fourteenth-century attention of famed Italian jurist Bartolus of
Sassoferrato and generations of late medieval Hungarian legists.133

128
See for example Menant, Campagnes lombardes, 59 and 176; Fumagalli, Landscapes,
104–105; Pinto, “Incolti, fiumi, paludi,” 1–7; Bravard, “Des versants aux cours d’eau”;
Levy, “Tant va la cruche à l’eau”; Rossiaud, La Rhône, 93–155; Molkenthin, “Der
Rhein,” 49–53.
129
Lewin, “Medieval environmental impacts and feedbacks,” 277–278. Lewin (p. 297)
stresses that natural physical forces drove changes in channel morphology, while human
activity more resulted in floodplain wetness and sedimentation, although the scale and
form of the latter also depended on local soil types.
130
Molkenthin, “Der Rhein,” 50; Trusen, “Insula in flumine nata.”
131
Berger and Brochier, “Rapports de la géoarchéologie”; Calvet et al., “Les cours d’eau
des Pyrénées orientales,” 286–287. Flood records from other French rivers, the Arno,
Po, and those of Germany share this general chronology (Grove and Rackham, Nature
of Mediterranean Europe, 133–136; Leguay, L’eau dans la ville, 399–406; Fumagalli,
Landscapes, 88–89, 110–112, and 117–121; Camuffo and Enzi, “Two bi-millenary
series”; and Bork et al., Landschaftsentwicklung, 237–249). But a very long-term study
of sediments dated by 14C found riverine flooding in coastal Iberia, southern France,
and Italy most frequent during the sixth/seventh, tenth, and late fifteenth centuries,
while the thirteenth and sixteenth were drier (Benito et al., “Holocene flooding,”
21–23).
132
Bravard et al., “La diversité spatiale des enregistrements morphosédimentaires”;
Rossiaud, Le Rhône, 128–137.
133
Bartolus wrote in his 1355 Tractatus de fluminibus “Travelling towards a certain villa
situated near Perugia above the Tiber, I began to contemplate … the changes of the

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 5 Aquatic Systems under Stress, c. 1000–1350 223

Perturbations in riverine hydrologies flow down to estuaries and the

sea. At the onset of the MCA in the tenth–eleventh centuries, upper and
middle reaches of the Wisła became unusually active, with clusters of
frequent flood events. In some areas a meandering morphology began to
braid.134 At the time this large basin drained into a delta and estuary
extending some sixty kilometers from Gdańsk east to Elbląg with bays,
wetlands, and channels reaching equally far inland and all loosely delin-
eated from the Baltic by a string of offshore islands. Archaeozoology
reveals a brackish environment with inshore schooling fishes. From the
thirteenth century and into the later Middle Ages this landscape evolved
into an increasingly drained delta on the west, where the river entered the
sea, and to the east a separate lagoon (Zalew Wislany, Frisches Haff )
fully enclosed by a continuous sand spit.135 Fourteenth-century villagers
along the lagoon shoreline there now took diadromous and freshwater
fishes (salmon, pike), while by the mid-1400s sea-caught cod had
become prominent in demesne fisheries of the ruling Teutonic Order.136
Coastal environments elsewhere experienced diverse variabilities.
Average global sea level remained relatively stable throughout the mid–
late Holocene, fluctuating only a meter or two. But local seismic activity,
post-glacial uplift, land subsidence, shoreline erosion, terrestrial drain-
ages, siltation, and shifts in storminess and normal wind direction vari-
ously affected medieval coastlines in several regions. Sweden’s Lake
Mälaren was a bay of the Baltic open to seagoing vessels in the Viking
Age and until about 1200, when post-glacial rebound raised it above
mean sea level so it became entirely fresh water and Stockholm replaced
Birka as the principal port. Salinity in the long, narrow estuary of the
Schlei fell significantly in the course of the twelfth century, so what trace
element analysis indicates were fishes taken locally ceased to be the

river-bed as well as a host of unanswered questions which I had come across in

practice …” Text of Bartolus’s prologue is in Cavallar, “River of law”; a complete
reprint of the 1576 printed edition is Bartolus, Tractatus de fluminibus, ed. Astuti. I am
grateful for the discussion of wandering rivers in the Pannonian plain by András Varas
in his (so far) unpublished dissertation, “Who stole the water? The control and
appropriation of water resources in medieval Hungary,” 153–172.
134
Starkel et al., “Past hydrological events,” 24, and Lewin, “Medieval environmental
impacts and feedbacks,” 270 and 301 (the latter citing Starkel, ed., Evolution of the
Vistula River Valley, vol. 1 (Warsaw: Polish Academy of Sciences, 1982), a text I have
not been able to consult).
135
Filuk, “Biologiczno-rybacka charakterystyka ichtiofauny,” 130–159.
136
Willam, “Fischerei des Deutschen Ordens,” 99–137 and 147–149; Martens,
Gartensiedlungen, 154–156, 202–205, 276–278, and 358; Sarnowsky, Wirtschaftsführung,
283–284.

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 224 The Catch

marine species, herrings and others, eaten at Haithabu before 1085.

Instead late medieval people barely five kilometers away at Schleswig
ate perch, bream, and pike.137
Along the southern shore of the North Sea, storms could turn land into
new arms of the sea. What had into the 1100s been a complex of
freshwater lakes, wetlands, rivers, and drained farmland had become by
the end of the 1200s a marine embayment, locally called the ‘South Sea’
(Zuiderzee). Land subsidence and storm floods broke the Frisian coastal
barrier at Texel in 1282, and five years later the Saint Lucia flood of
14 December washed deep inland to drown tens of thousands of people
and untold livestock, replacing thousands of hectares of pasture and
arable with salty waters. While subject to intermittent storm surges, the
new sea’s boundaries stabilized in the fifteenth century and lasted into
the twentieth.138 Storm waves from a different direction washed deep
into drained wetlands of the Thames estuary in the 1230s, 1280s,
1320s,1334, and 1370s; once people stopped trying restore the damage,
the newly enlarged salt marsh increased local fish habitats and fisheries
there expanded, especially after 1351.139 On the other hand, the Bay of
the Somme which had reached to Abbeville twenty kilometers inland,
was by 1300 receding together with its fisheries for eel and flatfishes, and
so, too, further south the once even larger ‘Gulf of Pictons’ in Poitou. Yet
on the other French coast, unstable passes and fluctuating salinity levels
of Languedoc lagoons motivated fishers and rights holders to adjust their
institutional relations and keep on fishing.140

137
Grupe et al., “A brackish water aquatic foodweb”; Becker and Grupe, “Archaeometry
meets archaeozoology.” Likewise at the northern tip of Jutland deposition of eroded
sand closed the Limfjord in the twelfth century, shifting its waters from a marine to a
freshwater or brackish habitat (Hybel and Poulsen, Danish Resources, 48–49).
138
Besides formation of the Zuiderzee, other well-known counter-examples to what
happened at the mouth of the Wisła occurred during the transition from the MCA to
the LIA. Large losses of human lives, arable, and villages along the North Frisian coast
from ‘de grote mandrenke’ (the great human drowning) of 17 January 1362, and similar
marine incursions recreated extensive areas of tidal flats and marshlands, productive
aquatic environments of the Wadden Sea (Meier, “From nature to culture,” 95–102,
attends to the losses). More cases are in Supplement 5.4.1.
139
James Galloway provides much local detail in his “Storm flooding”; “London and the
Thames estuary,” 130–135; “Storms, economic and environmental change,” 388–391;
and “Expansion or eclipse?”. Bailey, “Per impetum maris,” describes coastal inundations
elsewhere in eastern England but not their effect on local fisheries.
140
Clavel, “Restes osseux animaux,” 200–202; Clavel and Cloquier, “Sources
documentaires et archéologiques,” 207–208; Abel, “Defining a new coast”; Bourin-
Derruau et al., “Le littoral languedocien au Moyen Âge,” 349–357; Carozza et al.,
“Lower Mediterranean plain accelerated evolution.” Provensal et al, “Geomorphic
changes,” explores the evolving Rhône delta.

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 5 Aquatic Systems under Stress, c. 1000–1350 225

Little recent or extant research on the history of climate or hydrology

has paid direct attention to aquatic habitats. The norm in water history
treats a physical fluid, not a biological substance. And indeed most any
efforts to relate these variables had until recently to contend with climate
data so broadly drawn (in both spatial and temporal terms) that conclu-
sions would be crude at best and more often misguided. Even with
increased palaeoscientific precision in assessing climatic variables, only
very occasionally during the Middle Ages are coincident biological and/
or economic archives of specific local fisheries sufficiently detailed to
allow even probable hypotheses. But to assume the aquatic realm of
medieval Europe was unchanging or driven only by human actions would
fly in the face of basic ecological knowledge. While leaving problems of
large commercial marine fisheries at the very end of the Middle Ages for
treatment in Chapter 8 below, shifting ranges and stocks of several
species on the continent and in the Baltic do appear consilient with
climatic and hydrographic fluctuations.

5.4.2 Traces of Impacts, Resilience, and Adaptation

In the context of varying medieval climates and weather with evident or
likely effects on regional and local aquatic systems, we can trace certain
fairly well documented changes in specific fish stocks to prior or simul-
taneous natural phenomena. At least two freshwater fishes may have
achieved their sometimes tenuous natural establishment in western
Europe under favourable conditions of the MCA and then, lacking
purposeful human intervention, barely survived the LIA there. Water
temperature, salinity, and oxygen content influenced interacting species
of considerable human interest in the medieval Baltic.
The rapid eleventh- through thirteenth-century spread already
observed of common carp across central and western continental
Europe was less evidently associated with people actually rearing fish –
nearly all records before the 1250s treat carp as wild – than with their
placing captured wild fish in ponds for live storage. This occurred during
what is now understood as a warm phase of the MCA, when mean
European annual and summer temperatures both peaked. Carp are
thermophilic organisms, meaning they do like heat. In the wild this
species begins to spawn in weedy shallows during May–June as water
temperatures move above 18 C. Reproductive success is restricted to
years when the water level starts rising in May and when high tempera-
tures and flooding of terrestrial vegetation last for a long period during
May and June. This is because carp larvae survive only in what is by
modern north European standards very warm water (at or above 20 C)

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 226 The Catch

among shallow submerged vegetation.141 Chapter 7 will show that later

European fish farmers learned to design special spawning ponds to warm
quickly and to handle the larvae with special care, but that came as the
climate cooled into the LIA. Carp’s prior high medieval expansion likely
benefitted as much from natural heat as it did from humans moving a
prospective fish dinner from one watershed to another.
Adult individuals of a small cyprinid, the bitterling, look very like
juvenile carp.142 Until about 1100 the known range of the bitterling
was restricted to southeastern Europe, more or less similar to the pre-
medieval range of the carp, though no one ever thought bitterling would
make a palatable meal. Bitterling are perhaps more thermophilic than
carp, preferring waters above 16 C by June and needing 23 C for suc-
cessful reproduction. The earliest records of bitterling in central and
western Europe occur in regions where carp were becoming known and
carp culture would later become significant (see Chapter 7). In the mid-
twelfth century Hildegard of Bingen, where the Nahe joins the middle
Rhine, even knew the bitterling’s love for warm water. Thereafter writ-
ten, visual, and archaeozoological traces of bitterling multiply in those
regions, only nearly to vanish after about 1550, while Europe endured
the coldest two centuries of the LIA. Bitterling reappear and spread only
from the late 1700s. While quite widely abundant in recent times, local
populations decline markedly following years and decades with cold
spring temperatures and revive with warmer ones as at the end of the
twentieth century. Like carp, then, bitterling spread westwards during
warm medieval summers with entirely inadvertent human assistance;
come the cooler state of the LIA the species contracted most of its
western range.143

141
Adult carp, however, tolerate even very cold conditions. Kottelat and Freyhof,
Handbook, 147–148; www.fishbase.org/summary/Cyprinus-carpio.html (consulted 20
December 2016).
142
What follows summarizes Van Damme et al., “Introduction of the bitterling,” with
added biological information from fishbase.sub Rhodeus-amarus (consulted
20 December 2016) and Kottelat and Freyhof, Handbook, 82–84. Some authorities
consider European Rhodeus amarus synonymous with R. seriecus, which has a widely
separate Asian distribution. The little fish drew attention for the ‘farting’ sound it makes
when handled and for the long tubular ovipositor the female deploys to insert her eggs
into freshwater mussels, where the larvae live as parasites. Recent debates are over the
bitterling’s indigenous status in western Europe and thus its qualification for special
protection under EU water regulations.
143
Dirk Heinrich explored in several articles probable connections between climatic
conditions and the discontinuous range in northwestern European watersheds of
another thermophilic species, catfish: “Fischreste als Quellengattung,” 176–178;
“Bemerkungen zur nordwestlichen Verbreitung des Welses”; “Information … from
tales,” 19–20; and “Methodological considerations,” 163–165.

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 5 Aquatic Systems under Stress, c. 1000–1350 227

Medieval evolution of herring and cod fisheries inside the Baltic may
owe more to natural variability than to human enterprise or impacts. To
recapitulate and anticipate: herring were abundant in the central and
southwestern Baltic (Bornholm, Pomerania, the Schlei) from the fifth/
sixth centuries into the thirteenth and by the latter date also in the Danish
straits (of which much more in Chapter 8). Cod were certainly present in
the Baltic during the Neolithic and again from the fourteenth century,
while during early and high medieval times this species is virtually absent
from the written and archaeozoological record there.144 The traditional
explanation is that Slavic peoples had no taste for cod but immigrants
from Germany did. Stable isotope and other studies of the cod bones
themselves, however, identify the oldest medieval cod remains found at
Haithabu and in the eastern Baltic as imports from the North Sea or
Norway, that is, as imported stockfish. Yet by the end of the Middle Ages
people in this region did plainly fish locally for cod.
More recent suggestions observe that known low salinity and hypoxic
(low oxygen) conditions in deep water basins of the medieval Baltic could
have suppressed cod populations. In the Baltic today strong hypoxic
conditions thought to arise from a westerly flow of wind and waters from
the Atlantic, a warming climate, and eutrophication from nutrient-rich
runoff place a cap of warmed fresh water on top of colder saltier waters
where no mixing occurs. This situation drives many free-floating eggs of
cod into the deepest basins where lack of oxygen prevents larval develop-
ment and so threatens cod recruitment.145 Baltic herring, however, like
their North Sea kin, breed in relatively warm, biologically productive, and
often brackish surface layers. Sediment cores demonstrate that hypoxia in
the Baltic is not just a modern but rather a recurring phenomenon, present

144
Heinrich, “Fang und Konsum” and “Fishing and consumption of cod”; Makowiecki,
“Studies on the evolution,” 176–179, “Catalog,” table 2, and “Usefulness of
archaeozoological research,” 109–110; Lõugas, “Fishing during the Viking Age” and
“Fishing and fish trade,” 111–112 and 114–115; Holm, “Commercial sea fisheries,”
18–19. Absence of cod remains from the early Viking Age site of Truso and from pre-
1200 Gdańsk, as well as the Atlantic origin of cod bones at Haithabu suggest that even
the Norse found few of the species in the early medieval Baltic (Makowiecki, “Janów
Pomorski”; Rulewicz, Rybołówstwo Gdańska, 61; Lepiksaar and Heinrich, Fischresten aus
Haithabu, 119; Schmölcke and Heinrich, “Tierknochen aus dem Hafen,” 220–233).
145
The analysis here proposed applies to evident medieval fluctuations in Baltic hydrology
and fish ecologies the observed late twentieth-century environmental and regime shifts
there as set out in detail by Hammer et al., “Fish stock development under hydrographic
and hydrochemical aspects,” 557–564, and briefly by Alheit and Pörtner, “Sensitivity of
marine ecosystems to climate and regime shifts,” 168. These refer to work by Mackenzie
et al., “Quantifying environmental heterogeneity”;MacKenzie et al., “Ecological
hypotheses,” 177–190; Köster et al., “Baltic cod recruitment”; Zillen et al., “Past
occurrences of hypoxia in the Baltic”; van der Lingen et al., “Trophic dynamics,”
135 and 145; and Brander, “Impacts of climate change on fisheries,” 393.

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 228 The Catch

both during the early Holocene (c. 9000–c. 5000 ybp) and roughly
between 550 CE and 1200  50 years. Thereafter bottom waters became
better oxygenated and remained so into the nineteenth century.146
Long-term changes in the state of the Baltic, termed a ‘regime shift’ by
recent ecologists, have been linked to climate variations. The earlier
medieval and the most recent condition of deep water hypoxia beneath
a warm surface layer of low salinity result from a positive NAO charac-
teristic of both the MCA and modern warming. Predominant westerlies
then push salt water in from the North Sea and raise precipitation levels
across the Baltic watersheds. Temperature and salinity differences
encourage stratification. Near-surface temperatures and biological prod-
uctivity are high. Fading of the MCA from around 1200 tended to bring
more negative NAO, with lower salinity but also lower temperatures and
nutrient levels. More balanced salinity and temperature allowed greater
mixing, so conveying more oxygen to the deep basins. Distinctive onset
of the LIA by around 1500 strengthened a negative NAO, produced drier
and colder conditions in central European lands, and prolonged the no
longer new marine trophic regime for another three centuries.
In the present-day Baltic abundant cod are the principal predator on
herring, which controls the herring population. Under modern conditions
of intensive fisheries, removal of predators results in superabundant prey
populations, a typical form of trophic cascade. With few cod present, early
medieval herring stocks could explode until limited by some other eco-
logical factor.147 Very recent ecological field work and theories even
suggest that, as herring will themselves predate on planktonic cod eggs
and larvae, the large medieval schools could (further?) have suppressed a
Baltic cod stock already under stress from low oxygen in the habitats
critical for its reproductive life stage. Both the abundance of adult cod
and cod recruitment show negative correlation with herring biomass.148

146
Zillén et al., “Past occurrences of hypoxia in the Baltic,” 87; Kuijpers et al., “Baltic Sea
inflow regime”; Weckström et al., “Palaeoenvironmental history of the Baltic”; and
Franke et al., “North Atlantic circulation.” During the LIA, in contrast, east-central
Europe experienced dry conditions and an unstable hydroclimate (Tylmann and
Grosjean, “Climate variability in Central and Eastern Europe”). For the conceptual
framework of ‘regime shifts’ used here return to Chapter 1, note 34.
147
Sparholt, “Fish species interactions”; Köster et al., “Baltic cod recruitment”; and
Heikinheimo, “Interactions between cod, herring and sprat.” Corten, Herring and
Climate, demonstrates the positive response of herring to warmer waters.
148
Fauchald, “Predator–prey reversal”; Van Denderen and Van Kooten, “Size-based
species interactions,” 3; and Sánchez-Garduño et al., “Role reversal.” On the
negative relationship in the twentieth-century North Sea see Engelhard et al., “ICES
meets marine historical ecology,” 1391–1394,” and works there cited. Auber et al.,
“Regime shift in an exploited fish community,” suggest synergy between exploitation
and climate change in driving regime shifts involving small pelagic species.

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 5 Aquatic Systems under Stress, c. 1000–1350 229

Based on organic and chemical markers in layered bottom sediments, the

accepted chronology for shifts in oxygen and salinity levels in the medieval
and early modern Baltic matches poorly with growth of human populations
and the intensity of land use in that watershed. The initial conditions which
would impact both cod and herring stocks were established well before high
medieval clearances in central Europe and Scandinavia could much have
affected the runoff regime. Indeed trends shift in the opposite direction just
as the wave of settlement and clearances began to crest in the north German,
Polish, and eastern river basins which provide the bulk of the sea’s fresh
water. Although properties of large enclosed water bodies change more
slowly than do atmospheric drivers, the southern Baltic herring fishery
spiraled into insignificance in the course of the 1200s, supplanted by surging
growth in the Danish straits. As Chapter 8 will trace closely, the latter fishery
endured some two centuries during the very time fishing for cod came
forward in many Baltic coastal areas. Those local cod fisheries would then
persist even as Øresund herrings faded before Dutch exploitation of North
Sea stocks under now stabilized LIA conditions. In sum, given what is now
known about habitat requirements and predator–prey relationships across
life cycles of cod and of herring, climatic and hydrological conditions in the
Baltic Sea during the central and high Middle Ages (the MCA) were
propitious for the latter species and stressful for the former. Climatic forces
thus appear to have been important drivers in the medieval Baltic oscillation
to and then from what one ecologist calls ‘a herring dominated state.’
Coastal societies exploited abundantly accessible stocks until natural
conditions slowly changed. As foreshadowed earlier in this chapter and
spotlighted in Chapter 8, the Baltic herring fishery of the tenth through
fifteenth centuries was quite probably medieval Europe’s largest single
source of marine protein.
And were Mediterranean waters and fishes unaffected? Have archae-
ologists and historians failed to ask the right questions in the most
record-rich region of medieval Europe? Or did the natural world simply
interest literate medieval Italian, Provençal, and Catalan elites even less
than it did those of the north? Nevertheless, good proxies indicate colder
Italian winters during the early 1300s and again in certain fifteenth-
century decades. We also do know that eighteenth-century fisheries for
Adriatic sardines fluctuated in tandem with weather patterns.149
~~~ <>< ~~~~ ><> ~~~

149
None of the essays in Buti et al., eds., Moissonner la mer (2018), or Tønnes Bekker-
Nielsen and Gertwagen, eds., The Inland Seas: Towards an Ecohistory of the
Mediterranean and the Black Sea (2016), or Mylona and Nicholson, eds., The Bountiful
Sea (2016) show any interest in Camuffo, “Freezing of Venetian lagoon,” 54; Camuffo

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 230 The Catch

At local and regional scale aquatic systems of high medieval Europe were
subject to multiple pressures and constraints across the interplay of nat-
ural and cultural forces. Relevant drivers and effects varied from one
socio-natural site to another. A widely evident rise in human environ-
mental impact had negative consequences for fishes with strict habitat
requirements, while favouring varieties more tolerant of heat, low oxygen,
and high nutrient levels. Changes of natural origin, a warmer climate and
more, also created, destroyed, or shifted equilibria among fish species,
with at least some effect on human use. Contemporary Europeans may
have been oblivious to some such variations or lacked the perspective to
see them in the longer term, but people plainly did become aware of
certain changes. Some traditional fisheries seemed less productive
(scarce) and other local stocks to offer fishers opportunities to respond
to greater demand for fish. Neither resource destruction and depletion nor
the dilemmas of allocation and conservation are peculiar to present-day
fisheries crises. The next chapter turns to responses in medieval commu-
nities to perceptions of limits, declines, and shortages in fishes Europeans
had long liked to eat, so exploring Europeans’ own cultural resilience and
adaptability. Reciprocal and reiterative interactions among medieval
European natures and cultures drove the larger narrative of fisheries to
be apprehended as collectivities of myriad socio-natural sites.

and Bertolin, “Climate in the Mediterranean,” 127; Benito et al., “Holocene flooding”;
Luterbacher et al., “Review of palaeoclimatic evidence”; or even the tight correlation of
Mediterranean clupeids (sprat, sardine, anchovy) with eastern Atlantic species driven
by the Atlantic Multidecadal Oscillation as shown in Alheit et al., “Atlantic
Multidecadal Oscillation (AMO) modulates dynamics.” But see Županović, Ribarstvo
Dalmacije, 37–131, notably 58–64, 90–98, and 145–158, despite its necessary
dependence on what are now obsolete weather reconstructions.

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