ISSN: 0001-5113 - AADRAY ACTA ADRIAT.

, 54(2): 273 - 282, 2013

Exploitation trends of the Mediterranean and Black Sea

fisheries
Athanassios C. TSIKLIRAS*, Anny DINOULI and Eleni TSALKOU

Laboratory of Ichthyology, Department of Zoology, School of Biology, Aristotle University of

Thessaloniki, UP Box 134, 541 24, Thessaloniki, Greece

*Corresponding author, e-mail: atsik@bio.auth.gr

The exploitation trends of Mediterranean and Black Sea fisheries stocks were examined using
the total annual catches, the variability of the mean trophic level of the catch and fishing-in-balance
index for the period 1970-2010. Overall catches increased rapidly to their maximum levels by the
late 1980s and then declined and remained rather stable at around 75% of their highest levels. The
mean trophic level of the catches followed a similar pattern to the overall catches with constant
(except for 2005-2007) but steady decline since the late 1980s. The annual catches of 2636 stocks
were also analysed for the period 1970-2010 and classified into exploitation categories according
to the catch-based method of stock classification. In 2010, about 22% of the stocks were depleted,
40% were overexploited, 24% were fully exploited while undeveloped/developing fisheries were
confined to 14%. All analyses indicate that the Mediterranean and Black Sea fisheries are gradually
contracting to unsustainable levels.

Key words: marine catches, trophodynamics, overfishing, Mediterranean Sea, Black Sea

Introduction the General Fisheries Commission for the Medi-

terranean (GFCM) records (in some cases, his-
Contrary to the north Atlantic for which torical catches are available: MOUTOPOULOS &
long-term time series of fisheries catch data are STERGIOU, 2011), while stock assessments and
available, at least for some species of high com- surveys usually concern a limited number of
mercial interest (e.g. herring Clupea harengus, species and are routinely performed within the
cod Gadus morhua: OJAVEER et al., 2007; plaice framework of international projects (e.g. less
Pleuronectes platessa: Cardinale et al., 2011), than four stock assessments from the Mediterra-
and stock assessments that may extend back nean and the Black Seas are included in the RAM
to 1800 (RICARD et al., 2012), such data for the Legacy Stock Assessment Database: RICARD et
Mediterranean and the Black Seas are scarce and al., 2012). The scarcity of catch and stock assess-
sporadically collected (PILLING et al., 2008; STER- ment data is more pronounced at the eastern and
GIOU & TSIKLIRAS, 2011). Catch (=landings for southern parts of the Mediterranean (STERGIOU
the purposes of this work) data for most Medi- & TSIKLIRAS, 2006), and for that reason, several
terranean and the Black Sea stocks are available Mediterranean areas have been characterized as
since 1950 through the Food and Agricultural fisheries data poor areas (PILLING et al., 2008).
Organization (FAO) and since the 1970 through Official fisheries catch statistics (such as
274  ACTA ADRIATICA, 54(2): 273 - 282, 2013

those recorded by FAO and GFCM) and recon- exploitation categories, based on the relation-
structed catches available from other sources ship between the catch of a given year to the his-
(e.g. Sea Around Us Project: CHASSOT et al., torical maximum catch. This method has been
2010) are considered proxies of stock size and extensively used to assess the status of fisheries,
have been widely used to uncover patterns and globally or on ecosystem basis (WORM et al., 2006;
trends in fisheries (CHRISTENSEN et al., 2003; PAULY, 2008; ZELLER et al., 2008; FROESE & KES-
MYERS & WORM, 2003; PINNEGAR et al., 2003; NER-REYES, 2009) and is a reliable indicator of
ZWOLINSLI & DEMER, 2012; PAULY et al., 2013; overexploitation especially when complemented
TSIKLIRAS et al., 2013). Since catch statistics may with fishing effort and ecological indices (TSIK-
be affected by fisher’s behaviour, market forces LIRAS et al., 2013). Its disadvantage is that it does
and fisheries regulations (MAUNDER & PUNT, not account for species that are, even partly, not
2004), stock assessments have been proposed as officially recorded (illegal, unreported, recrea-
a more reliable proxy of stock biomass, because tional and subsistence catches) but are affected
they are often fishery independent and contain by fishing; thus, the output of the method is a
intensively collected biological data (HILBORN conservative estimate of the true stock condition
& WALTERS, 1992). However, as previously men- because it refers to a portion of its catch.
tioned, stock assessments are only available for The aim of the present work was to assess
a small proportion of exploited stocks, which the exploitation status of the Mediterranean and
in the Mediterranean and the Black Sea is even Black Seas fisheries stocks for the period 1970-
smaller (LLEONART, 2005). In addition, stock 2010, using a catch-based method and compare
assessment data are expensive to collect and them with the corresponding global trends (e.g.
time consuming to analyze, especially across SUMAILA et al., 2007) and/or similar work per-
trophic levels and habitats (they are usually con- formed elsewhere (e.g. TSIKLIRAS et al., 2013).
fined to demersal stocks), when compared to the The analysis was complemented with the tem-
freely available official catch statistics. Thus, poral variability of the total catches, the number
the immediate availability of catch records of recorded stocks, the mean trophic level of the
provides a first indication of change in stock catches, and the fishing-in-balance index.
biomass that can be later confirmed or rejected
through a detailed stock assessment or survey. Materials and methods
The use of fisheries catch data and catch-
based methods for evaluating the state of a The annual catches, expressed as live weight
fishery is important in the Mediterranean and equivalent of landings, have been routinely
the Black Sea for scientific and socio-economic recorded since 1970, for the Mediterranean and
reasons, as the area is bordered by over 25 coun- the Black Sea combined (FAO area 37), by the
tries, belonging to three continents, resulting to General Fisheries Commission for the Mediter-
a multi-cultural puzzle with varying levels of ranean (GFCM: FAO, 2013). The Mediterranean and
fisheries technologies and management regula- the Black Sea area has been further subdivided
tions (PAPACONSTANTINOU & FARRUGIO, 2000; into four fishing subareas (western, central, east-
LLEONART, 2005), but also to test environmental/ ern Mediterranean Sea and Black Sea) and ten
climatic hypotheses (e.g. emigration of tropi- fishing subdivisions (TSIKLIRAS et al., 2010). The
cal species through Suez Canal: GOLANI, 1998). GFCM data refer to the legal and reported large-
This multi-cultural puzzle imposes the use of and small-scale fisheries catches, excluding
common methodology that can be achieved discarded catch, illegal, unreported, recreational
through official catch statistics. Therefore, in the and sport fishing. For the present analysis, catch
present work, the catch-based method of stock statistics of the Mediterranean and the Black Sea
classification (FROESE & KESNER-REYES, 2002; were extracted using FISHSTAT-J (FAO, 2013) from
KLEISNER et al., 2012) was used in order to clas- the GFCM Capture Production database for 2636
sify the Mediterranean and Black Sea stocks into records (or stocks, defined as species-area-coun-
 TSIKLIRAS et al.: Exploitation trends of the Mediterranean and Black Sea fisheries... 275

try combinations) for the period 1970-2010. where Y refers to the total catches in year
The annual status of fisheries (1970-2010) k, mTLc is the mean trophic level of the catch-
was classified into one of the following five cat- es, TE is the mean energy-transfer efficiency
egories: undeveloped, developing, fully exploit- between trophic levels that is assumed to be
ed, overexploited, and depleted according to the 0.1, and 0 refers to the first year in a time-series
catch-based stock classification method (FROESE that is used as a baseline (in present dataset,
& KESNER-REYES, 2002; KLEISNER et al., 2012). 1970, the beginning of records, was set as a
The classification was based on the relation- baseline). FiB attains a value of 0 for the first
ship between the catches (CY) of a given year year of the series and remains rather stable when
(YC) compared to the year (YCmax) of historical trophic level and catches change in opposite
maximum catch (CMAX). Thus, in an unde- directions. Increasing FiB values indicate geo-
veloped fishery, YC<YCmax and CY<0.1CMAX; graphic or bathymetric expansion of fisheries,
in a developing fishery, YC<YCmax and while decreasing FiB values indicate contraction
0.1CMAX<CY<0.5CMAX; in a fully exploited fish- (PAULY et al., 2000).
ery, CY>0.5CMAX; in an overexploited fishery, Since the fishing effort was available for
YC>YCmax and 0.1CMAX<CY<0.5CMAX; and, in a a very short period of time and consistently
collapsed fishery, YC>YCmax and CY<0.1CMAX. recorded as number of boats, engine horsepower
The former two categories (undeveloped and and tonnage only for some countries of the
developing) were combined in the analysis, Mediterranean Sea (LLEONART, 2005), it was not
which included only the stocks with sufficient included in the analysis.
consecutive records. The analysis was separate-
ly performed to stocks that were present since Results
1970, i.e. those with 40 consecutive records.
Complementary to the catch-based classifi- Number of stocks
cation, two trophodynamic indicators were also
explored: the mean trophic level of the catches The number of recorded fisheries stocks
and the Fishing-in-Balance index. The mean in the Mediterranean and Black Sea increased
weighted trophic level of the catch (mTLc) for linearly (r2=0.96) from 1222 in 1970 to 1925
each year (k), was calculated using the trophic in 2010 (Fig. 1A). The rate of increase in stock
levels of each species (taken from FishBase and records for the entire study period was around
SeaLifeBase: FROESE & PAULY, 2011; PALOMARES 18 records per year, i.e. the catches of 18 new
& PAULY, 2011), as (PAULY et al., 1998): stocks were being separately recorded each year.

Catches


Overall, the combined marine fisheries
catches of fishes, crustaceans and cephalopods
of the Mediterranean and the Black Sea ranged
where Yi refers to the catches of a species (or between 1.1×106 (in 1970) and 1.99×106 (in
group of species) i, and TL is the corresponding 1988) t. Since 1988, they declined by about 25%
trophic level. to 1.42×106 t in 2010. During the last decade the
The fishing-in-balance index (FiB) of the combined Mediterranean and Black Sea catches
catch for each year was calculated as follows fluctuated around 1.5×106 t (Fig. 1B).
(PAULY et al., 2000):
Trophodynamics

The mean weighted trophic level of the

Mediterranean and Black Sea catches (mTLc)
276  ACTA ADRIATICA, 54(2): 273 - 282, 2013

Fig. 1. Basic trends of the Mediterranean and Black Sea

fisheries for the period 1970 to 2010. The number of
stocks recorded by GFCM Capture Production per
year (A), the combined marine catches of fishes, crus-
tacean and cephalopods (B), the mean trophic level
(mTLc) of the catches (C), the Fishing-in-Balance
(FiB) index (D) and the trend in the status of fisher-
ies resources according to the catch-based method
(FROESE & KESNER-REYES, 2002) and the official
FAO-GFCM statistics (E).

down. The tendency of mTLc is declining since

1988, with three outlying values compared to
the overall declining trend (2005, 2006, 2007).
fluctuated between 3.28 (in 1975 and 2003) and The declining rate of mTLc was 0.02 per decade
for 1990-2010.
3.38 (in 2007), with a value of 3.25 in 2010 (Fig.
The fishing-in-balance index increased rap-
1C). Overall, mTLc decreased from an average
idly from 1970 (FiB=0, baseline) to a maxi-
value (±SD) of 3.33 (±0.024) for 1970-1979 to mum value of 0.318 in 1988 and then declined
an average value (±SD) of 3.30 (±0.038) for sharply to 0.089 in 1991 (Fig. 1C). Since then,
2001-2010, thus confirming that the Mediterra- FiB fluctuated around 0.15 with a mean value of
nean and Black Sea food webs have been fished 0.13±0.055 for the last decade (Fig. 1D).
 TSIKLIRAS et al.: Exploitation trends of the Mediterranean and Black Sea fisheries... 277

Stock classification Discussion

Based on the historically maximum catch, The increasing number of recorded stocks
which varied among the Mediterranean and with time (Fig. 1A) indicates either the exploita-
Black Sea stocks included in the analysis, in tion of new species, or the separate recording
2010, out of the 1798 available stocks, 400 of catches of species that had been previously
(22.3%) were depleted, 711 (39.5%) were over- recorded aggregated to higher taxonomic levels.
exploited, 428 (23.8%) were fully exploited In any case, the increasing number of records
and 259 (14.4%) were developing (Fig. 1E). with time artificially increases the contribution
In the early 1970s, the majority of stocks had of developing stocks in the analysis, thereby
been largely underexploited and most fisheries reducing the remaining categories. Thus, some
(over 75%) were developing (Fig. 1E). Only a developing stocks may well have been fully
few stocks were overexploited and even fewer exploited or even overfished based on their
were depleted. Over the last 20 years, however, previous catches that were reported aggregated.
an increasing percentage (averaging 35.8% for The separate analysis on the stocks with 40
2001-2010) of stocks suffers from overexploita- consecutive records confirms the bias towards
tion. The cumulative percentage of overfished developing stocks.
and crashed stocks rapidly increased from 10%
The total Mediterranean and Black Sea
in 1976, to 20% in 1984, 30% in 1989, 40% in
catches were increasing from 1970, peaked in
1995, 50% in 1999 and around 60% in 2004. In
1985-1988 and since then, they have declined
contrast, the percentage of developing stocks
by 25% and remained rather constant since late
declined dramatically, from around 80% in
1990s (Fig. 1B). This decline coincides with
1970 to 14.4% in 2010. Interestingly enough,
the slow, albeit steady, declining rates of the
the percentage of fully exploited stocks has
mean trophic level of the catches, which also
remained rather unchanged since 1970 (averag-
occurred after the mid 1980s (Fig. 1C). Since
ing 22.9±2.15% for 1970-2010).
Generally, in 2010, most Mediterranean and the decline in trophic level occurs at low rates
Black Sea stocks belonging to large-bodied spe- (also reported by PAULY et al., 1998, but based
cies were overexploited or depleted (data not on a longer time series, that of Global Capture
shown), irrespectively of their habitat prefer- Production for FAO Area 37: FAO, 2011), then
ences (i.e., pelagic, demersal or reef-associated). the fishing-in-balance (FiB) index is deter-
For example, the majority of large pelagic (e.g. mined by the fluctuation of catches (PAULY et
garfish Belone belone), demersal (e.g. European al., 2000). Hence, their similar pattern of decline
hake Merluccius merluccius), and reef-associat- is a clear sign of fisheries contraction in the
ed (e.g. dusky grouper Epinephelus marginatus) Mediterranean and the Black Sea (PAULY et al.,
stocks were overexploited/depleted. However, 2000; TSIKLIRAS et al., 2013). The Mediterranean
there were some medium- (e.g. blue whit- and the Black Sea stock analysis in the present
ing Micromesistius poutassou, common dentex work was combined merely for comparability
Dentex dentex) and small-sized taxa (e.g. bogue purposes, but, given the different environmental
Boops boops, the picarels Spicara spp.) that and fishing properties of these two seas (FAO,
were also overexploited irrespectively of their 1997; DASKALOV, 2002), a further investigation
habitat (data not shown). of their fisheries status may be necessary on a
When the analysis was performed to stocks subarea or even subdivision basis. The irregular
that had been recorded since 1970 (i.e. with 40 values of 2005, 2006 and 2007 are the result of
consecutive records), in 2010, more stocks were variable taxonomic aggregation in various areas
depleted (27.2%) and overexploited (51.5%) (e.g. Libya, Montenegro) and catch fluctuations
compared to fully exploited (17.0%) and devel- of the small pelagic fishes (anchovy, sardine and
oping (4.3%). round sardinella) in the central Mediterranean
and the Black Sea. These irregularities were also
278  ACTA ADRIATICA, 54(2): 273 - 282, 2013

apparent in the stock classification to exploita- marginatus and common dentex Dentex dentex
tion categories (Fig. 1E). were either depleted or overexploited, a state
Previous research on the exploitation status that also emerged for some of them through their
of Mediterranean and Black Sea fisheries stocks detailed stock assessments (LLEONART, 2005).
report that, in the Mediterranean, 78% of the The intensive and selective removal of species
stocks are fully exploited, whereas the 85% of with slow life-history strategies by fishing may
the stocks are overexploited in the Black Sea reduce biodiversity, both within and among
(DASKALOV, 2002; SHERMAN & ADAMS, 2010). species, and affect the ecosystem structure and
According to another report, 60% of the Medi- functioning (PAULY et al., 1998; BIRKELAND &
terranean and Black Sea stocks were fully DAYTON, 2005), i.e., may lead to ecosystem over-
exploited during 1951-1960, but soon recovered fishing (MURAWSKI, 2000). The stocks of large
(FROESE & KESNER-REYES, 2002). The remaining pelagic fishes, such as those of the bluefin tuna
40% had been overfished by that time but never Thunnus thynnus and swordfish Xiphias gladius,
fully recovered in the following 30 years (FROESE have also been reported as overexploited (LLE-
& KESNER-REYES, 2002). Similar research using ONART, 2005), but because they are subjected to
the catch-based method but applied on a differ- Total Allowable Catch regulations, they cannot
ent dataset (that of Global Capture Production be classified based on their catches and were
for FAO Area 37, which extends back to 1950, excluded from the analysis.
instead of GFCM Capture Production for the The variability in catches of small pelagic
Mediterranean, which extends back to 1970: fishes may be related to their complex interre-
FAO, 2013) reports that over 80% of the Medi- lationships (e.g. the anchovy/sardine complex:
terranean stocks are fully exploited, but only a KATARA et al., 2011), which, in turn, may be the
few are depleted (AQUARONE et al., 2008). The result of environmental or climatic forces on
situation is even worst for the Black Sea, where their distribution and abundance (e.g. round
around 90% of the stocks have been reported as sardinella Sardinella aurita: TSIKLIRAS, 2008).
collapsed for 2004 (Heileman et al., 2008, using Thus, when fishing effort data are not available
the FAO Global captured production). Finally, and detailed knowledge of the stock dynamics is
a recent work on the Greek fisheries showed lacking, it is difficult to disentangle the climatic
that, in 2007, 65% of them were overfished and and fishing effects and the interpretation of such
32% were fully exploited (TSIKLIRAS et al., 2013). cases should be cautious (ZWOLINKSI & DEMER,
No depleted stocks were observed in the Greek 2012). Besides small pelagic fishes, the over-
waters and only 3% of them were develop- exploitation status of demersal medium- and
ing. Overexploitation of Greek marine fisheries small-sized species shows that fishing gradually
resources has been reported to occur across taxa, penetrates to lower trophic levels either directly,
sizes and habitats, with several small-bodied by targeting smaller ones (STERGIOU & TSIK-
species being overfished (TSIKLIRAS et al., 2013). LIRAS, 2011; TSIKLIRAS et al., 2013), or indirectly
Life-history theory predicts that large-bod- by by-catching them. However, by-catch bio-
ied, long-lived and slow growing species are mass removal cannot be easily quantified from
more susceptible to overexploitation (ADAMS, catch statistics, or from stock assessments.
1980; FROESE & KESNER-REYES, 2002). Indeed, In order to reverse overexploitation trends
most demersal and reef-associated Mediterrane- in the Mediterranean and the Black Seas, near
an and Black Sea stocks, i.e. those characterized future fisheries management scenarios should
by slow life-history strategies, were among the focus on the preservation of ecosystem health by
most heavily exploited across the study area, a strictly enforcing current regulations, limiting
trend that is supported by theoretical and empiri- fishing effort, banning excessive subsidies, and
cal data (JENNINGS et al., 1998; REYNOLDS et al., excluding a large part of current fishing grounds
2005). Almost all stocks of European hake Mer- from any fishing activity (PAULY et al., 2002).
luccius merluccius, dusky grouper Epinephelus
 TSIKLIRAS et al.: Exploitation trends of the Mediterranean and Black Sea fisheries... 279

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Received: 18 March 2012
Accepted: 28 September 2013
 TSIKLIRAS et al.: Exploitation trends of the Mediterranean and Black Sea fisheries... 281

Trendovi iskorištavanja živih bogatstava Sredozemnog i Crnog mora

Athanassios C. TSIKLIRAS*, Anny DINOULI i Eleni TSALKOU

Laboratorij za ihtiologiju, Zavod za zoologiju, Odsjek za biologiju

Sveučilište Aristotel u Solunu, P.P. 134, 541 24, Solun, Grčka

* Kontakt adresa, e-mail: atsik@bio.auth.gr

SAŽETAK

Trendovi iskorištavanja živih bogatstava Sredozemnog i Crnog mora su analizirani pomoću

ukupnih godišnjih ulova, varijabilnosti prosječne trofičke razine ulova te uravnoteženosti ribolovnog
indeksa za razdoblje 1970.-2010. U kasnim 1980-im ukupni ulov se naglo povećao do svoje
maksimalne moguće razine, a zatim je došlo do pada te je ostao prilično stabilan na razini od oko
75% od svoje najveće razine. Prosječne trofičke razine ulova slijede sličan obrazac ukupnih ulova
s konstantnim (osim za razdoblje 2005.-2007.) i stalnim padom od kraja 1980-ih godina. Godišnji
ulovi 2636 iskorištavanih stockova također su analizirani za razdoblje od 1970. do 2010. godine i
podijeljeni prema eksploatacijskim kategorijama. U 2010. godini oko 22% zaliha živih bogatstava
je bilo iscrpljeno, 40% se prekomjerno iskorištavalo, a 24% je doseglo maksimalnu razinu
iskorištavanja. Sve analize upućuju na to da je iskorištavanje živih bogatstava Sredozemnog i Crnog
mora doseglo maksimalne vrijednosti, pa čak u nekim slučajevima i do neodržive razine.

Ključne riječi: ulov, živa bogatstva, dinamika trofičkih odnosa, prelov, Sredozemno more,
Crno more
282  ACTA ADRIATICA, 54(2): 273 - 282, 2013