ICES CM 2004 / CC: 06

ESTIMATION OF BIOMASS, PRODUCTION AND FISHERY POTENTIAL OF OMMASTREPHID SQUIDS IN THE WORLD OCEAN AND PROBLEMS OF THEIR FISHERY FORECASTING

Ch. M. Nigmatullin

Atlantic Research Institute of Marine Fisheries and Oceanography (AtlantNIRO), Dm. Donskoj Str. 5, Kaliningrad, 236000 Russia [tel. +0112-225885, fax + 0112-219997, e-mail: squid@atlant.baltnet.ru]

ABSTRACT

21 species of the nektonic squids family Ommastrephidae inhabits almost the entire waters of the World Ocean. It is the most commercial important group among cephalopods. Straight and expert evaluations of biomass were carried out for each species. In all ommastrephids the total instantaneous biomass is ~55 million t on average and total yearly production is ~ 400 million t (production/biomass coefficient - P/B = 5 in inshore species and 8 - in oceanic ones). Now there are 12-fished species, mainly 8 inshore ones. In 1984-2001 the yearly world catch of ommastrephids was about 1.5-2.2 million t (=50-65% of total cephalopod catch). The feasible ommastrephids fishery potential is ~ 6-9 million t including 4-7 million t of oceanic species. Thus ommastrephids are one of the most important resources for increasing high-quality food protein catch in the World Ocean. At the same time there are serious economical and technical difficulties to develop oceanic resources fishery, especially for Ommastrephes and Sthenoteuthis. A general obstacle in the real fishery operations and fishery forecasting for ommastrephids is their r-strategist ecological traits, related to monocyclia, short one-year life cycle, pelagic egg masses, paralarvae and fry, and accordingly high mortality rate during two last ontogenetic stages. So, the stock size 2 dynamics and distribution are associated with environmental variability. In this context the problem of fisheries forecasting has special significance. These problems of forecasting for short (< 0.5 month), medium (0.5-12 months) and long (> one year) terms are briefly described on the examples of results of Soviet/Russian investigations.

Key words: ommastrephid squids, World Ocean, biomass, production, ecological traits, fishery forecasting

INTRODUCTION

Ommastrephid squids are the most abundant, widely distributed and ecologically active group of cephalopods. In cephalopods fishery their current and future role is extremely important. During the latest three decades the proportion of these squids in the world catch of cephalopods has been permanently amounted to more than a half (FAO, 2003). The future increase of cephalopods catch is primarily connected to this group of squids also.

Until now no attempts of complex estimation of the total biomass, production and fishery potentials of cephalopods have been actually made. At the same time these estimates are necessary for assessment of cephalopods fishery development prospects and their role in the World Ocean ecosystem. At present this is especially actually, since neither apparent resources of marine objects fishery increase in the World Ocean are available on the basis of fishery intensification on already exploited stocks (Moiseev, 1989; FAO Mar. Res., 1997).

The purpose of this report is to estimate in the first approximation the scale of biomass, production, potential catch and ecosystem role of inshore (Table 1, No 1-15) and oceanic (Table 1, No 16-21) representatives of ommastrephid squid on the basis of own observations and literature data.

MATERIAL AND METHODS

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Biomass of common oceanic squids (Table 1, No 16-19) has been estimated primarily on the basis of mass direct visual observations and counts, and obtained density values (kg/km2) were extrapolated to poorly researched areas (reviews: Zuev et al., 1985, 2004; Nesis, 1985; Nigmatullin et al., 1991). Data for several inshore species (Table 1, No 1-7, 10, 13) were obtained from the literature (review: Nesis, 1985) and mainly from own estimates of biomass in the areas with high abundance on the basis of the trawling surveys data and commercial statistics. Biomass estimates of other species are based on trawl catch data extrapolation taking into account quantitative distribution peculiarities. Therefore, estimates of most non-commercial species are mainly of expert nature and only approximate. All ommastrephids are monocyclic typical r-strategists with one-year life cycle. They are characterized with considerable long-term fluctuations of abundance (by the order of magnitude or more). Where possible, the minimum and maximum estimates of the species biomass are presented. As a matter of fact the actual biomass fluctuations are much wider. Biomass values obtained in this work are close to the mean in the common situations.

The annual production values were estimated on the basis of production/biomass (Р/В) coefficient equal to 5 in inshore (Nesis, 1985) and 8 in oceanic species (Laptikhovsky, 1995). To estimate food consumption the minimum diurnal ration of adult nektonic ommastrephids (5% of the body weight) was used (Zuev et al., 1985, 2004; O’Dor & Wells, 1987). All calculations were based on the squid specimens above 8-12 cm in mantle length. The usual mantle length of most squid species is 15-40 сm, and the maximum length is up to 60-90 сm.

RESULTS AND DISCUSSION

Total stock size and annual production

The extended distribution area of ommastrephids covers the most part of the World Ocean from Sub-Arctic to Sub-Antarctic, including waters of the shelf, slope and 4

open ocean from the surface to the depths of 1000-2000 m. Almost all species, particularly the oceanic ones, are abundant and widely distributed. Therefore, the obtained estimates of ommastrephids biomass and production (Tables 1, 2) are maximum for large mass abundant oceanic species. The minimum and maximum biomass values for given species of inshore squids differ by a factor of 2, those of oceanic by 1.3 and common – by 1.5 (Table 2). Dynamic of numbers of the most abundant ommastrephids in different ocean areas occur mainly in the opposite phase; therefore maximum values of summarized estimates (Table 2) seem unrealistic. Apparently, the following intermediate values are more realistic: total biomass ~55 million t, production ~400 million t, food consumption ~1 000 million t.

Table 1. Approximate values of instantaneous biomass (IB) of ommastrephids squid, in million tons

No Species IB No. Species IB 1 Illex illecebrosus 1-3 15 Ornithoteuthis volatilis 1.0 2 Illex coindetii 1-2 16 Dosidicus gigas 8-10 3 Illex argentinus 2-5 17 Ommastrephes bartramii 10-13.5 4 Todaropsis eblanae 1-2 North Pacific 3-3.5 5 Todarodes pacificus 2-5 North Atlantic 2-2.5 6 Todarodes sagittatus 1-2 South Pacific 2-2.5 7 Todarodes angolensis 0.5 Indian Ocean 1-1.5 8 Todarodes filippovae 0.5 South Atlantic 2-3.5 9 Todarodes sp. (Southeastern 0.5 18 Sthenoteuthis pteropus 4.2-6.5 Pacific) 10 Nototodarus sloanii 1-1.5 19 Sthenoteuthis oualaniensis 8-11.2 11 Nototodarus gouldi 0.5-1 Indian Ocean 3-4.2 12 Nototodarus hawaiiensis 0.5 Pacific Ocean 5-7 13 Martialia hyadesi 1-3 20 Eucleoteuthis luminosa 0.5 14 Ornithoteuthis antillarum 0.5 21 Hyaloteuthis pelagica 0.3

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Table 2. Approximate values of instantaneous biomass (IB), annual production and annual food consumption (by daily feeding rate = 5% BW) of ommastrephids squid, in million tons

Ecological group IB P/B- Annual Annual food coefficient production consumption Inshore (species No 1-15) 14-28 5 70-140 255-511

Oceanic (species No 16-21) 31-42 8 248-336 565-766

Total 45-70 - 318-476 820-1277

The general remarks on ecosystem role

The total annual food consumption by cephalopods is estimated as 2 000-4 000 million t (Rodhouse, Nigmatullin, 1996), while its share consumed by ommastrephids constitutes 25-50% (Table 2). Taking in account the high rate of general metabolism, daily consumption rate (6-12% of the body weight of adult squids) and the rate of somatic and generative growth of ommastrephids (O’Dor, Wells, 1987; Zuyev et al., 2002) the above considerations are quite realistic.

From the point of view of the progressive consumers evolution criterion by V.I. Vernadsky – E.S. Bauer, which is determined by the rate and the scale of matter and energy transformation per time unit by animals, they are the leaders among nektonic animals in the rate and scale of matter and energy transformation and biogenic migration of chemical elements. In the absence of squids, the rate of matter and energy flows in ecosystems slows down. Owing to the unique combination of such parameters as high abundance, biomass, production, food consumption, total and active metabolism, short life cycle and highly diversified trophic relations, ommastrephids play the role of “accelerators” of the biogeocenological processes, they are some kind of specific “ecosystem enzymes” (Nigmatullin, 2000). 6

During the life cycle, with a body size increase, most ommastrephids “permeate” the trophic pyramid, consecutively transferring from consumers of II-III orders to consumers of IV-VI orders and respectively changing the spectrum of their food organisms, enemies and parasites. In some oceanic communities adult ommastrephids are actually top predators. They are characterized by long daily vertical (hundreds meters) and ontogenetic horizontal migrations both parallel (up to 1000-1500 miles) and perpendicular (bathymetric migrations) to the coast line. During these migrations squids crossed the boundaries of various climatic zones and ecosystems. Owing to the above considerations ommastrephids have the role of one of the most important elements in the “rigid framework” of high mobile predators, that has integrated the local ecosystems into the ecosystems of the higher rank, and finally into the whole ecosystem of the World Ocean, being at the same time the important element of the Ocean’s homeostasis mechanism.

Total fishery potential

In 1990-2001 the world catch of cephalopods amounted to 2.4-3.4 million t, while ommastrephid catch was 1.5-2.2 million t, or 50-65% of the total catch (FAO, 2003). The level of inshore Ommastrephidae exploitation, including mainly representatives of Illex, Todarodes and Nototodarus, (about 2 million t per year) is close to the maximum and any significantly increase of the catch at these group seems unlikely in principle.

In 1997-1999 the proportion of oceanic species constituted only 6-10% of ommastrephid catch (FAO, 2003). Out of them only Neon flying squid (Ommastrephes bartramii) in the North Pacific and Jumbo flying squid (Dosidicus gigas) in the Gulf of California and off Peru are commercially exploited. The bulk of populations of oceanic squids Ommastrephes and Sthenoteuthis are scattered. The dense potentially fishable aggregations amounted to about 4-7 million t of Dosidicus, Ommastrephes and Sthenoteuthis.

The total fishery potential of ommastrephids is estimated as 6-9 million t, while the total cephalopods potential amounted to 6-12 million t (Moiseev, 1989). In general, 7 the oceanic ommastrephids are only unique abundant reserve in the World Ocean for the increase in world commercial catch of high-quality food protein. These stocks may be exploited on the all-year-round basis if the problems of optimization of fishery aggregations search, methods of artificial “condensing” of fished squids and more effective fishing methods and tactics, as well as wasteless catch utilization are solved. However, at the first stage of these problems solution considerable financial support and scientific efforts will be required.

Fishery forecasting: Russian results

One of the most important factors determining the pattern of abundance dynamics and distribution of ommastrephid exploitable stock is the availability of planktonic larvae and fry inhabiting subsurface water layer for about 2-2.5 months. These stages are characterized with the maximum mortality rate; therefore they primarily determine recruitment level. Another most important ecological-population parameter of these squids is one-year life cycle. These two factors stipulate problems and specifics of ommastrephids fishery forecasting.

The temporal scales of ommastrephids population life cycles are incomparable with those of medium- and long-living polycyclic teleosts. This results in different temporal criteria of ecological-fishery forecasting advance time: short-term – from 1-3 days to 0.5 month, medium term – from 0.5 to 8-12 months and long-term – from 12 months to several decades.

In short-term forecasting in addition to monitoring of squid aggregation’s biological state (different indices depending on feeding or spawning state of the aggregation), the data on habitat of fishery concentration trends and affecting factors are also important. The optimal predictors are dynamics of T-S traits distribution for specific water mass, location and intensity degree of frontal zones based on micro- survey and control hydrological transects data. If these works are impossible to fulfill, the relationships between atmospheric circulation indices and catch per effort are used. In 1980s these approaches had been developed for the Argentine shortfin squid Illex argentinus fishery in the fishery ground of 45-47° S outside the Argentine EEZ in South-West Atlantic (Polishchuk, 1987, 1988, 1991, 2002). 8

Two approaches are applied in medium-term forecasts in Illex argentinus fishery. The first approach is based on the data of monitoring catches and age-length structure of Illex argentinus in successive locations along pre-spawning migration route in April-June (for 0.5-1 month: Arkhipkin, 1993) or relationship between catches in the first (February) and the second (May) half of given fishing season (for 2-3 months: Nigmatullin, Laptikhovsky, 1996). The second approach is based on the retrospective data, i.e. on revealed relationships between satellite SST data in spawning and recruitment formation areas and catches during this year-class exploitation 5-8 months later (Illex argentinus in Southwestern Atlantic: Devitsyn et al., 2001; Laptikhovsky et al., 2001, 2002 и Angola flying squid Todarodes angolensis on the shelf of Namibia: Nigmatullin et al., 2000).

Long-term forecasts are based on the analysis of relationship between long-term sets of data on catches and environmental factors, including mainly atmospheric and subsurface water circulations. Yu.M. Froerman (1981, 1985, 1986) was a pioneer in long-term forecasts development by the example of shortfin squid Illex illecebrosus in the Northwestern Atlantic (relationship between the Gulf Stream dynamics and squid recruitment abundance). The similar cycle of investigations was carried out with Japanese flying squid Todarodes pacificus from the Northwestern Pacific (reviews: Murata, 1989; Mokrin, 2004), as well as a preliminary estimation of Todarodes angolensis from the shelf of Namibia (relationship between intensity of Benguella upwelling and squid catches: Pljakin, 1991; Laptikhovsky et al., 1992). Such forecast is possible only if the forecast of environmental factors limiting population dynamics is available. Unpredictable combinations of environmental factors (variability of environmental “window” parameters or “demographic bottleneck”) resulting in larvae mortality at the early development stages, affect negatively the forecast. Besides, in conditions of restricted fishing areas (available fishing ground is the part of more wide fishing range) and high stock abundance the aggregations distribution and their availability to fishery may become the major factor of fishery efficiency. At present the long-term prediction of this factors is rather difficult.

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CONCLUSIONS

Estimation of instantaneous ommastrephid biomass using traditional trawling and jig long-line surveys and quantitative visual counting at night stations requires considerable inputs of vessel time to cover extended areas, while the initial results interpretation involves serious methodical problems resulting in significant errors in estimates obtained. In this respect, implementation of the acoustic method (Goss et al., 2001; Starr, Thorne. 1998) in ecologic-fishery researches of squids with parallel control trawling or long-line stations seems very promising. Unfortunately this method does not reduce the uncertainty inherent in the final results, however it has an important advantage, i.e. this method allows to obtain the required information from extended areas during relatively short time period. At the same time each squid species requires a special adaptation with methodical aspects adjustment, first of all the target strength value and its variability assessment and adaptive methodology for optimal survey track selection.

On the basis of initial data of quantitative visual counting of oceanic species and catch per effort of trawls and long-lines, the instantaneous biomass of 21 ommastrephid species, being most important in cephalopods fishery and in the World Ocean ecosystem, has been estimated for the first time. On this basis the production and food consumption by inshore and oceanic ommastrephids have been estimated to the first approximation. In general, the total biomass of these squids is estimated as 45-70 million t (~55 million t on average), the annual production - 318-476 million t (~400 million t) and annual food consumption - 820-1277 million t (~1 000 million t), including the respective estimates for 15 coastal species: 14-28 million t, 70-140 million t and 255-511 million t, and for 6 oceanic species: 31-42 million t, 248-336 million t and 565-766 million t. Certainly these estimates are of expert and highly approximate nature. However, they provide a relatively realistic idea about the scales of ommastrephid phenomenon and their role in the ocean life.

The following comparisons may give a general idea about the estimates obtained. The proportion of ommastrephids in the total biomass of cephalopods (200- 375 million t: Rodhouse, Nigmatullin, 1996) and all pelagic cephalopods (150-300 million t: Nesis, 1985) equal to 15-27% and 18-35% respectively. Ommastrephids 10 constitute only 4.5% of the total biomass of large-sized teleosts, however the level of their annual production is similar (Moiseev, 1989). The total production of ommastrephids is close to that of mesopelagic cephalopods (350-700 million t: Nesis, 1985). Ommastrephids constitute about 1% of the total nekton biomass (6 000 million t: Moiseev, 1989), but 10% of their total production. The share of ommastrephids amounts to 0.2-0.3% of the total biomass (20 000-25 000 million t) and 0.06-0.08% of the total production (70 000-80 000 million t) of the all-living animals of the World Ocean (Moiseev, 1989).

Owing to the unique combination of ecologic-physiological traits, ommastrephids are one of the most important elements of the "rigid frame" of highly mobile predators that unites local ecosystems into ecosystems of the higher rank and they functions as a kind of "ecosystem enzymes" in the World Ocean ecosystems.

The feasible ommastrephids fishery potential is ~6-9 million t including ~4-7 million t of oceanic species. Thus ommastrephids are one of the most important resources for increasing high-quality food protein catch in the World Ocean.

In 1970s-1980s the extensive complex data on environment conditions, ecological parameters of fished populations and fishery were collected. They allowed developing several approaches to fishery forecasting with various advance time. However, during the latest 15 years the lack of parallel hydro-meteorological, population-ecological and fishery data sampling became the principle obstacle in ommastrephid ecological-fishery forecasting. In these situation utilization of available maps of baric (atmosphere circulation) situations, satellite SST data and altimetry data on sea level anomaly, as well as the data on the Earth rotation velocity and its inclination angle constitute the main directions of fishery forecasting investigations.

ACKNOWLEGEMENTS

My heartily thanks to K.N. Nesis, G.V. Zuev, R.N. Burukovsky, A.N. Vovk, Yu.M. Froerman, O.P. Ovcharov, V.N. Nikolsky, M.A. Pinchukov, A.I. Arkhipkin, 11

V.A. Bizikov, S.I. Bazanov, A.V. Parfenjuk, V.V. Laptikhovsky, R.M. Sabirov and A.S. Shchetinnikov for many years collaboration and useful discussions.

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