Fisheries Research 54 (2001) 38

Managing and forecasting squid sheries in variable environments

P.G. Rodhouse*
British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK

Abstract
Squid are short-lived ecological opportunists which generally have a lifespan of about 1 year. Their populations are labile
and recruitment variability is driven, to a greater or lesser extent, by the environment. This variability provides a challenge to
management because sheries for short-lived species are best managed by effort limitation and it is difcult to set effort on a
rational basis in the absence of information about the abundance of the next generation prior to recruitment. However, recent
research has shown that recruitment variability in several squid species can be partly explained by environmental variability
derived from synoptic oceanographic data. In the eastern Pacic coastal upwelling system a shery for Dosidicus gigas has
grown rapidly during the last decade and abundance and catch rates seem to be linked to the El Nino/southern oscillation
(ENSO) cycle. ENSO is one of the best understood ocean/climate systems and so with increased knowledge of the life cycle
biology of D. gigas, this shery may provide a good model for understanding environmentally driven recruitment variability in
exploited squid populations. # 2001 Elsevier Science B.V. All rights reserved.
Keywords: Squid; Fisheries; Management; Forecasting; Environmental variability

1. Introduction
The world squid catch has increased substantially
over the last two decades in response to increasing
demand for seafood during a period when catches of
traditionally exploited species have started to level off
or decline (Rodhouse, 2001). There is evidence to
suggest that as the abundance of some groundsh
stocks has been reduced through overshing, stocks
of squid which are short-lived ecological opportunists have increased due to reduced predation
pressure from the sh and relaxed competition for
food (Caddy and Rodhouse, 1998). The squid sheries
are, therefore, of interest not only because of their
growing importance as a source of high quality protein

*
Tel.: 44-1223-221612; fax: 44-1223-362616.
E-mail address: pgkr@pcmail.nerc-bas.ac.uk (P.G. Rodhouse).

for human consumption but also because of their

possible role as indicators of global ecological change
driven by shery exploitation in the oceans.
Populations of short-lived, semelparous (spawn
once and die), opportunistic species, such as squid
are typically unstable, responding rapidly to changes
in environmental conditions. The squid sheries,
therefore, present challenges for managers who are
concerned with maintaining stable recruitment and
optimum catch rates. On the other hand, because squid
populations are more labile than populations of longlived sh, which have high inertia because of the
damping effect of the presence of several year classes
living contemporaneously, they are a better model
for understanding environmentally driven variable
recruitment.
This short review aims to demonstrate the importance of being able to predict recruitment strength
and future stock size for the management of squid

0165-7836/01/$ see front matter # 2001 Elsevier Science B.V. All rights reserved.
PII: S 0 1 6 5 - 7 8 3 6 ( 0 1 ) 0 0 3 7 0 - 8

P.G. Rodhouse / Fisheries Research 54 (2001) 38

sheries. It describes recent advances that have been

made in forecasting squid sheries, and illustrates
the potential for developing knowledge further by
studying the sheries in the coastal upwelling systems
of the eastern Central Pacic. This is a key region
inuenced by the variability of the El Nino/southern
oscillation (ENSO) system, which is probably the
best understood ocean/climate phenomenon on earth.
For this reason, the Dosidicus gigas shery may,
in due course, prove to be a reasonably predictable
squid shery with respect to recruitment strength
and abundance.
2. Management methods
The life cycle characteristics of squid present particular problems for shery management. The problem is that after one generation of squid has spawned
and died there is initially no information on which to
base an assessment of the potential recruitment
strength and abundance of the next generation. A
meaningful catch quota cannot, therefore, be set until
the forthcoming generation has passed through the
egg, larval and early juvenile phases and has recruited
into the shery. In view of these problems, Caddy
(1983) proposed that squid sheries should be managed by effort limitation, instead of by quota, and
assessed and managed in real-time.
This approach was later adopted for management of
the Illex argentinus and Loligo gahi sheries in the
South Atlantic around the Falkland Islands (Malvinas)
(Beddington et al., 1990; Rosenberg et al., 1990;
Basson et al., 1996). Here, shing effort is controlled
by licensing a limited number of vessels of known
catching power and excluding unlicensed vessels.
Effort is set on the basis of pre-season surveys and
previous experience of recruitment variability. When
the shery is opened, the stock is assessed continuously by means of the LeslieDelury depletion
method. A target escapement, in terms of a minimum
allowable spawning biomass, is set and if the depletion
model predicts that the target escapement will not be
achieved if shing continues, the shery is closed.
A similar approach, using the LeslieDelury depletion model and target escapement, has recently been
used in the Mexican shery for D. gigas in the Gulf of
California (Morales-Bojorquez et al., 2001).

3. Forecasting recruitment
3.1. Ommastrephid squid
The processes of setting effort and licensing vessels,
in a shery being managed using this approach, have
to take place shortly before shing commences.
Clearly the ability to predict recruitment, even relatively crudely, early in the pre-recruit phase would
give managers and operators of vessels the advantage
of being able to plan in advance.
Bakun and Csirke (1998) have proposed a set of
hypotheses about how variability in ocean ecosystems
might cause inter-annual variability in the stocks of
ommastrephid squids that inhabit the major western
boundary current systems of the world's oceans. They
propose that recruitment may be dependent on one or
more of: (a) wind effects, with onshore, wind-driven
Ekman transport being favourable to both onshore
transport of surface dwelling larvae and offshore
migration of pre-adults in the sub-pycnocline layers;
(b) uctuations in prey abundance; (c) `matchmismatch' effects driven by temperature as proposed for
sh stocks by Cushing (1975); (d) variations in predation pressure; (e) disease.
In the South Atlantic, Waluda et al. (2001) have shown
by analysis of remotely sensed sea surface temperature
(SST) data that about 55% of variability in recruitment
strength in the Falkland Islands I. argentinus shery can
be explained by variation in the total area of surface
water of putative optimum water temperature for larval
development on the spawning grounds during the
spawning season prior to recruitment. This species
spawns in the vicinity of the Brazil/Falkland (Malvinas)
current conuence off the edge of the continental shelf
at the northern limit of the Patagonian Shelf. The SST
conditions that predict strong recruitment are also
associated with a reduced incidence of horizontal
temperature gradients (38C over 15 km) in the spawning area. SST variability in the South Atlantic has been
shown to have teleconnections with ENSO events in the
Pacic, so it is reasonable to conclude that variability
in the I. argentinus population probably has links back
to ENSO (Waluda et al., 1999).
Variability in abundance of Todarodes pacicus in
the Sea of Japan is also driven by changes in optimum
SST for larval development (Sakurai et al., 2000). In
this region, variability occurs on a decadal time-scale

P.G. Rodhouse / Fisheries Research 54 (2001) 38

and is apparently linked to large-scale climate changes

in the north Pacic.
3.2. Loliginid squid
In contrast to the ommastrephid squid, the life
cycles of loliginid squid are not linked to basin scale
oceanic circulation and their life style is more closely
linked to the seabed. Nevertheless, variability in
Loligo vulgaris vulgaris in the English Channel has
been shown to be correlated with inter-annual changes
in SST conditions (Robin and Denis, 1999) and in
South Africa, variable abundance of another loliginid
squid, Loligo vulgaris reynaudii, is apparently driven
by storm events during the spawning season. Storms
reduce underwater visibility on the spawning grounds
and reduce breeding success (Roberts and Sauer,
1994; Roberts, 1998). The explanation for this is that
squid possess excellent eyesight and have evolved
ritualised mating behaviour which is dependent on
being able to read the `body language' of potential
mates (Sauer et al., 1997). After storm events underwater visibility is poor so mating success is reduced
and this in turn has a negative effect on the spawning
success of the population.
In another study of variable recruitment strength,
Agnew et al. (2000) have shown that 66% of the
variance in recruitment strength in L. gahi in the
Southwest Atlantic can be explained by SST 6 months
prior to recruitment. Furthermore, a model combining
SST and spawning stock size explained 77% of the
variance, with very high spawning stock biomass
apparently leading to a reduction in recruitment
strength and suggesting a density-dependent effect.
This seems paradoxical because density-dependent
effects, in sh stocks for instance, are caused by
cannibalism hence the Ricker stock recruitment
model (Ricker, 1954). However, in squid such as L.
gahi the parent generation dies after spawning and is,
therefore, not present to cannibalise the next generation when it starts to grow so the proposed densitydependent mechanism must presumably be different.
4. Eastern pacic coastal upwelling system
It has been known for some time that predators,
especially sperm whales (Clarke et al., 1988), consume

large quantities of D. gigas off Peru in the coastal

upwelling system of the Peru Current. Until relatively
recently the stock had not been exploited other than by
a small-scale artisanal shery. In the late 1980s, shing vessels from the former Soviet Union started large
scale exploitation of the species (Nigmatullin et al.,
2001) and then in the early 1990s Far Seas squid
jiggers from east Asia (Japan and Korea) began to
exploit the stock on a much larger scale than previously (Yamashiro et al., 1998).
Whereas the other major sheries for ommastrephid
squids exploit stocks that inhabit the major high
velocity western boundary systems of the Atlantic
and Pacic Oceans, the D. gigas stock is located in
the relatively weak ow of the eastern boundary
current off the west coast of the Americas (Anderson
and Rodhouse, 2001). This oceanographic system is
characterised by highly variable coastal upwelling
which is directly inuenced by the ENSO system of
the tropical Pacic (Diaz and Markgraf, 2000).
Since the start of large-scale exploitation by the east
Asian eet off Peru the catch rate has uctuated
dramatically. This has apparently been in response
to changing environmental conditions associated with
ENSO. The high catch rates of the early 1990s
declined during the cold La Nina event which preceded the exceptional 1997/1998 El Nino (Yamashiro
et al., 1998). Catch rates began to increase again after
that El Nino.
The Pacic ENSO system is one of the best understood variable oceanographic systems in the world and
with predictive models that are increasingly able to
forecast an ENSO event in advance (Diaz and Markgraf, 2000), the D. gigas shery, and potentially sheries for other cephalopod species such as L. gahi, off
Peru should provide a very useful model for shery
forecasting.
5. Requirements for prediction
Research on predicting the response of squid
recruitment processes to environmental variability
must be based on a full understanding of the life cycle
biology of the species concerned. It is probably most
critical in particular to have detailed information about
the early life phase, from egg to post planktonic
juvenile. The eggs of ommastrephids and the larvae

P.G. Rodhouse / Fisheries Research 54 (2001) 38

of both ommastrephids and loliginids are planktonic

and hence subject to variable ocean current systems,
and this is probably the phase in the life cycle which is
most sensitive to environmental variability. Analysis
of recruitment patterns in both T. pacicus (Sakurai
et al., 2000) and I. argentinus (Waluda et al., 1999,
2001) has revealed that variability in abundance of the
adult phase can be explained by environmental variability which is temporally and spatially associated
with the early life phase. No correlation between
environmental variability and abundance could be
found when the environmental conditions experienced
by the adult phase of I. argentinus were analysed by
Waluda et al. (1999).
In the Peru Current, the life cycle of D. gigas is
beginning to be well characterised. Research by Russian scientists during the Soviet era (Nigmatullin et al.,
2001) has recently been supplemented by new data,
presented at the First International Symposium on
Pacic Squids at the VIII Congreso Latinamericano
de Ciencias del Mar, on distribution (Taipe et al.,
2001), maturation and spawning (Tafur et al., 2001)
as well as growth and population structure (Arguelles
et al., 2001). Recent research by Japanese scientists
working in the Peru Current system has also contributed new information on growth (Masuda et al., 1998)
and diurnal vertical migration in D. gigas (Yatsu et al.,
1999). Elsewhere in the East Central Pacic new data
have been collected in the Gulf of California on
reproduction of D. gigas (Markaida and Sosa-Nishizaki, 2001) and shery biology (Morales-Bojorquez
et al., 2001).
Furthermore, new data on parasites of D. gigas
(Schukhgalter and Nigmatullin, 2001) provide a
potential new tool for examining stock structure,
and advances in acoustic assessment of squid stocks
provides the potential for rapid, large-scale assessment
of biomass both before and after recruitment (Goss
et al., 2001).
Although an understanding of the life cycle of D.
gigas is beginning to emerge more data are needed on
the planktonic phases of the life cycle. In particular,
knowledge of the timing of appearance of the larvae,
their distribution and transport by currents needs to be
improved.
The biology and life cycle of L. gahi in Peruvian
waters is less well understood but this is being
addressed and recently data have been collected on

growth and shery biology of the species in the region

(Villegas, 2001). There is also a growing body of
literature on the species from the Southwest Atlantic
(Hateld and des Clers, 1998). To what extent information from the Southwest Atlantic, which lies close
to the sub-Antarctic Front, might apply to the situation
in the Peru Current is not clear but it would be sensible
to assume that the differing environmental conditions
between the two areas might be responsible for substantial differences in the biology and life cycle.
Knowledge of life cycle biology is best advanced by
hypothesis testing. The complex detail in the life
cycles of many species hampers the deductive
approach, whereas testing simple working hypotheses
can allow rapid progress. The life cycles of several
species are now well-known and these can provide
well tested models from which to develop new hypotheses for poorly understood species. Anderson and
Rodhouse (2001) propose a testable working hypothesis for the life cycle of D. gigas in the Peru Current
and also propose a hypothetical mechanism for how
recruitment variability might be driven by the ENSO
cycle. These hypotheses now need to be developed and
tested in the light of incoming data.
6. Conclusions
Squid are ecological opportunists and their abundance can uctuate widely between generations which
generally have a lifespan of about 1 year. These
uctuations are apparently environmentally driven
and there are numerous reports of `plagues' of squid
and other cephalopods in populations which are
unexploited, or only lightly exploited and so not
affected by shing pressure (Gunther, 1936; Rees
and Lumby, 1954; Nesis, 1983; Ehrhardt, 1991). There
are also well documented examples of large interannual uctuations in abundance in stocks exploited
by sheries (O'Dor, 1993; Sakurai et al., 2000;
Waluda et al., 1999, 2001). These observations suggest the terrestrial analogy of the desert locust whose
populations uctuate dramatically reaching plague
proportions and creating famine from biblical times
to the present (Skaf et al., 1990).
Recent studies are indicating that statistically signicant percentages of variability in recruitment and
abundance of squid can be explained by variability in

P.G. Rodhouse / Fisheries Research 54 (2001) 38

environmental parameters (Roberts, 1998; Robin and

Denis, 1999; Waluda et al., 1999, 2001; Agnew et al.,
2000; Sakurai et al., 2000). This research raises the
question of whether there is potential for forecasting
squid recruitment in the sheries. If in the future it
proves possible to provide reliable, if crude, forecasts
of future recruitment strength this would have considerable benet for managers of effort-limited sheries by providing an objective basis for setting effort
in advance of recruitment of the squid into the shery.
Although management measures might have relatively less inuence on recruitment success than the
environment in exploited populations of short-lived
squid, sheries must continue to be managed under
precautionary principles (FAO, 1996). Future research
on environmentally driven recruitment variability and
stock forecasting may be advanced by increasing
research effort on variability in the D. gigas stock
in the Peru Current system. Environmental variability
in this system is driven by one of the best understood
atmosphere/ocean systems in the world's oceans and
the shery, which is very well monitored by the
Instituto del Mar del Peru (IMARPE) observer programme, provides an excellent model for this research.
Acknowledgements
I thank Miguel Rab for being my personal guide in
Peru on many memorable occasions.
References
Agnew, D.J., Hill, S., Beddington, J.R., 2000. Predicting recruitment strength of an annual squid stock: Loligo gahi around the
Falkland Islands. Can. J. Fish. Aquat. Sci. 57, 24792487.
Anderson, C.I.H., Rodhouse, P.G., 2001. Life cycles, oceanography
and variability: ommastrephid squid in variable oceanography
environments. Fish. Res. 54, 133143.
Arguelles, J., Rodhouse, P.G., Villegas, P., Castillo, G., 2001. Age,
growth and population structure of the jumbo ying squid
Dosidicus gigas in Peruvian waters. Fish. Res. 54, 5161.
Bakun, A., Csirke, J., 1998. Environmental processes and
recruitment variability. In: Rodhouse, P.G., Dawe, E.G.,
O'Dor, R.K. (Eds.), Squid Recruitment Dynamics. The Genus
Illex as a Model. The Commercial Illex Species. Inuences on
Variability. FAO Fisheries Technology Paper No. 376, 273 pp.
Basson, M., Beddington, J.R., Crombie, J.A., Hoolden, S.J.,
Purchase, L.V., Tingley, G.A., 1996. Assessment and manage-

ment of annual squid stocks: the Illex argentinus shery as an

example. Fish. Res. 28, 329.
Beddington, J.R., Rodenberg, A.A., Crombie, J.A., Kirkwood, G.P.,
1990. Stock assessment and the provision of management
advice for the short n squid shery in Falkland Islands waters.
Fish. Res. 8, 351365.
Caddy, J.F., 1983. The cephalopods: factors relevant to their
population dynamics and to the assessment of stocks. In:
Caddy, J.F. (Ed.), Advances in Assessment of World Cephalopod Resources. FAO Fisheries Technology Paper No. 231,
pp. 416452.
Caddy, J.F., Rodhouse, P.G., 1998. Do recent trends in cephalopod
and groundsh landings indicate widespread ecological change
in global sheries. Rev. Fish Biol. Fish. 8, 431444.
Clarke, R., Paliza, O., Aguayo, A., 1988. In: Pilleri, G. (Ed.),
Sperm Whales of the Southeast Pacic. Part IV. Fatness, Food
and Feeding. Investigations on Cetacea, Vol. XXI, pp. 53195.
Cushing, D.H., 1975. Marine Ecology and Fisheries. Cambridge
University Press, Cambridge, 271 pp.
Diaz, H.F., Markgraf, V. (Eds.), 2000. El Nino and the Southern
Oscillation. Multiscale Variability and Global and Regional
Impacts. Cambridge University Press, Cambridge, 496 pp.
Ehrhardt, N.M., 1991. Potential impact of a seasonal migratory
jumbo squid (Dosidicus gigas) stock on a Gulf of California
sardine (Sardinops sagax caerulea) population. Bull. Mar. Sci.
49, 325332.
FAO, 1996. Precautionary approach to capture sheries and species
introductions. FAO Technical Guidelines for Responsible
Fisheries, No. 2. FAO, Rome.
Goss, C., Middleton, D., Rodhouse, P.G., 2001. Investigations of squid
stocks using acoustic survey methods. Fish. Res. 54, 111121.
Gunther, E.R., 1936. A report on oceanographical investigations in
the Peru coastal current. Discovery Rep. 13, 107276.
Hateld, E.M.C., des Clers, S., 1998. Fisheries management and
research for Loligo gahi in the Falkland Islands. CalCOFI
Report No. 39.
Markaida, U., Sosa-Nishizaki, O., 2001. Reproductive biology of
jumbo squid Dosidicus gigas in the Gulf of California, 1995
1997. Fish. Res., 54, 6382.
Masuda, S., Yokawa, K., Yatsu, A., Kawahara, S., 1998. Growth
and population structure of Dosidicus gigas in the Southeastern
Pacic Ocean. In: Okutani, T. (Ed.), Large Pelagic Squid.
Marine Fishery Resources Center, Tokyo, pp. 107118.
Morales-Bojorquez, E., Cisneros-Mata, M.A., Nevarez-Martnez,
M.O., Hernandez-Herrera, A., 2001. Review of stock assessment and shery biology of Dosidicus gigas in the Gulf of
California, Mexico. Fish. Res. 54, 8394.
Nesis, K.N., 1983. Dosidicus gigas. In: Boyle, P.R. (Ed.),
Cephalopod Life Cycles: Comparative Reviews, Vol. I.
Academic Press, London, pp. 215231.
Nigmatullin, Ch.M., Nesis, K.N., Arkhipkin, A.I., 2001. A review
of the biology of the jumbo squid Dosidicus gigas (Cephalopoda: Ommastrephidae). Fish. Res. 54, 919.
O'Dor, R.K., 1993. Big squid, big currents and big sheries. In:
Okutani, T., O'Dor, R.K., Kubodera, T. (Eds.), Recent
Advances in Cephalopod Fisheries Biology. Tokai University
Press, Tokyo, pp. 385396.

P.G. Rodhouse / Fisheries Research 54 (2001) 38

Rees, W.J., Lumby, J.R., 1954. The abundance of Octopus in the

English Channel. J. Mar. Biol. Ass. UK 33, 515536.
Ricker, W.E., 1954. Stock and recruitment. J. Fish. Res. Board Can.
11, 559623.
Roberts, M.J., 1998. The inuence of the environment on chokka
squid Loligo vulgaris reynaudii spawning aggregations: steps
towards a quantied model. S. Afr. J. Mar. Sci. 20, 267284.
Roberts, M.J., Sauer, W.H.H., 1994. Environment: the key to
understanding the South African chokka squid (Loligo vulgaris
reynaudii) life cycle and shery? Antarct. Sci. 6 (2), 249258.
Robin, J.P., Denis, V., 1999. Squid stock uctuations and water
temperature: temporal analysis of English Channel Loliginidae.
J. Appl. Ecol. 36, 101110.
Rodhouse, P.G., 2001. World squid resources. In: Review of the
State of World Fishery Resources: Marine Fisheries. FAO,
Rome., in press.
Rosenberg, A.A., Kirkwood, G.P., Crombie, J.A., Beddington, J.R.,
1990. The assessment of stocks of annual squid species. Fish.
Res. 8, 335349.
Sakurai, Y., Kiyofuji, H., Saitoh, S., Goto, T., Hiyama, Y., 2000.
Changes in inferred spawning areas of Todarodes pacicus
(Cephalopoda: Ommastrephidae) due to changing environmental conditions. ICES J. Mar. Sci. 57, 2430.
Sauer, W.H.H., Roberts, M.J., Lipinski, M.R., Smale, M.J., Hanlon,
R.T., Webber, D.M., O'Dor, R.K., 1997. Choreography of the
squid's `nuptual dance'. Biol. Bull. 192, 203207.
Schukhgalter, O.A., Nigmatullin, C.M., 2001. Parasitic helminths
of jumbo squid Dosidicus gigas (Cephalopoda: Ommastrephidae) in open waters of the Central East Pacic. Fish. Res. 54,
95110.

Skaf, R., Popov, G.B., Roffey, J., 1990. The desert locust: an
international challenge. Phil. Trans. R. Soc. London B 328,
525538.
Tafur, R., Villegas, P., Rabi, M., Yamashiro, C., 2001. Dynamics of
maturation, seasonality of reproduction and spawning grounds
of the jumbo squid Dosidicus gigas (Cephalopoda: Ommastrephidae) in Peruvian waters. Fish. Res. 54, 3350.
Taipe, A., Yamashiro, C., Mariategui, L., Rojas, P., Roque, C.,
2001. Distribution and concentrations of jumbo ying squid
(Dosidicus gigas) off the Peruvian coast between 1991 and
1999. Fish. Res. 54, 2132.
Villegas, P., 2001. Growth, life cycle and shery biology of Loligo
gahi (d'Orbigny, 1835) off the Peruvian coast. Fish. Res. 54,
123131.
Waluda, C.M., Trathan, P.N., Rodhouse, P.G., 1999. Inuence of
oceanographic variability on recruitment in the genus Illex
argentinus (Cephalopoda: Ommastrephidae) shery in the
South Atlantic. Mar. Ecol. Prog. Ser. 183, 159167.
Waluda, C.M., Rodhouse, P.G., Podesta, G.P., Trathan, P.N., Pierce,
G.P., 2001. Oceanography of Illex argentinus (Cephalopoda:
Ommastrephidae) hatching grounds and inuences on recruitment variability. Mar. Biol., in press.
Yamashiro, C., Mariategui, L., Rubio, J., Arguelles, J., Tafur, R.,
Taipe, A., Rab, M., 1998. Jumbo ying squid shery in Peru.
In: Okutani, T. (Ed.), Large Pelagic Squid. Japan Marine
Fishery Resources Center, Tokyo, pp. 119125.
Yatsu, A., Yamanaka, R., Yamashiro, C., 1999. Tracking experiments of the jumbo ying squid, Dosidicus gigas, with an
ultrasonic telemetry system in the eastern Pacic Ocean. Bull.
Nat. Res. Inst. Far Seas Fish. 36, 5560.