Managing and forecasting squid fisheries in variable environments

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 fisheries for short-lived species are best managed by effort limitation and it is difficult 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 Pacific coastal upwelling system a fishery for Dosidicus gigas has grown rapidly during the last decade and abundance and catch rates seem to be linked to the El Niño/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 fishery may provide a good model for understanding environmentally driven recruitment variability in exploited squid populations

Large and meso-scale distribution of the Ommastrephid squid Martialia hyadesi in the Southern Ocean: a synthesis of information relevant to fishery forecasting and management

The seven star flying squid, Martialia hyadesi, is a Southern Ocean ommastrephid with an oceanic distribution that extends to the edge of the shelves and slopes of continents and islands. Its range is circumpolar and it is generally associated with the Antarctic Polar Frontal Zone. It has been caught in commercial quantities in the Atlantic sector but is only recorded in smaller numbers from the Indian Ocean and Pacific sectors in scientific samples, the gut contents of predators and in mass strandings on island shores. It has only occasionally been found in commercial catches outside the Atlantic sector. In the northern part of its range in the South Atlantic, commercial catches are highly variable and apparently linked to large-scale oceanographic variability. Martialia hyadesi appears to concentrate in frontal areas where characteristics of the bathymetry generate meso-scale oceanographic features. Such concentrations have been observed at shelf breaks and in the deep ocean near a submarine ridge. Predator data confirm the circumpolar distribution of the species and its relationship with the APFZ. Grey-headed albatrosses appear to forage for M. hyadesi in the region of meso-scale oceanographic features associated with the bathymetry of submarine ridges and the shelves of oceanic islands. In the medium future, improved understanding of oceanographic variability of the Southern Ocean may provide the basis for long term forcecasting in a fishery for the species. In the nearer future, improved knowledge of the behaviour of the species in relation to meso-scale oceanography may provide the basis for short-term forecasting of the location of shoals based on remotely sensed images of surface oceanography. The life cycle of M. hyadesi is poorly understood and, in view of increased commercial interest in the species in recent years, and its conservation value in the CCAMLR area, there is a need for more information on the location of spawning and feeding grounds and seasonal migrations

Precautionary measures for a new fishery on Martialia hyadesi (Cephalopoda, Ommastrephidae) in the Scotia Sea: an ecological approach

In anticipation of the development of a new fishery for the ommastrephid squid Martialia hyadesi in the Scotia Sea, this paper presents a revision of annual consumption of the species by higher predators and provides a brief review of information about the life cycle and distribution of the species obtained from research fishing and commercial catches. This species is eaten by seals, whales and seabirds, the latter being the most reliable source of consumption data because comprehensive sampling can be carried out during their breeding seasons. A conservative estimate for total annual consumption of M. hyadesi by higher predators in the Scotia Sea is 245 000 tonnes, with an upper estimate of 550 000 tonnes if less reliable data are included. M. hyadesi spawns between autumn and mid-summer with peak hatching in winter/spring. Its life span has not been established. Data from the CCAMLR Convention Area suggest that M. hyadesi may live for two years, but this may vary. In common with other ommastrephids, the species is probably semelparous. It is proposed that the timing and catches of the fishery should be highly conservative and set taking into account the timing of breeding and consumption rates of the most sensitive of the dependent species. Most Antarctic predators which have been studied consume relatively small and immature specimens of M. hyadesi. Fishing for M. hyadesi after the chick-rearing period of the most sensitive predator (grey-headed albatross) would minimise competition locally and ensure that the fishery only exploited the stock after escapement from most higher predator species. It would also allow seabird predation of the stock to be monitored prior to the fishing season as a way of assessing numbers of pre-recruits. Closing the fishery before recruitment of the next generation of squid would ensure availability of prey to higher predators during the following chick-rearing period. Preliminary data from a squid jigger which undertook research fishing around South Georgia in June 1996 provided the basis for determining realistic potential catch rates

Todarodes filippovae in the Southern Ocean: an appraisal for exploitation and management

Todarodes filippovae Adam 1975 is a large oceanic ommastrephid squid with a pelagic distribution. It is closely related to T. angolensis but allozyme data have shown that the two species are separated by about the same genetic distance as other ommastrephid congenerics. T. jilippovae itself may comprise more than one species. It is reported to be widespread in the Southern Ocean from sub-Antarctic waters to north of the subtropical Front, but there are gaps in its known distribution which cast doubt on the conspecificity of the different populations. Squid identified as T. filippovae inhabit the open ocean up to the continental slope and they appear not to extend into shelf waters. Distribution of the various populations seems to be Jinked to the high velocity regions of the Antarctic Circumpolar Current, Falkland Current, Benguela Current and East Australia Current and these are probably important for transport of planktonic eggs and paralarvae and for the productive mesoscale features that these highly dynamic systems provide for adult feeding. Beaks attributed to T. filippovae have been found in the gut contents of sperm whales (Physeter catodon), southern elephant seals (Mirounga leonina), fish (Merluccius australis polylepis) and possibly by albatrosses (Diomedea melanophrys); however, there are insufficient data to estimate the annual consumption by known predator species. The juveniles feed on crustaceans, whereas the adults feed primarily on fishes and other cephalopods. In common with many other squid, they probably occupy a broad trophic niche. Knowledge of the life cycle is very incomplete. Spawning occurs in the Tasman Sea and off South Africa and probably takes place in the austral autumn and winter. The life span may be up to two years. Fishery potential has not been established, but in the Tasman Sea commercially viable catch rates have been reported. Effective exploitation and rational management of T. filippovae, or filippovae species/subspecies complex, requires research on species identification and stock structure, a full understanding of the life cycle of the different populations, knowledge of the relations between ocean currents, mesoscale oceanographic processes and biology, and a better understanding of role in the diet of higher predators

Adelieledone, a new genus of octopodid from the Southern Ocean

The syntypes of the endemic Southern Ocean octopodid Pareledone polymorpha (Robson, 1930) were re-examined and measurements, counts and indices are presented. The two forms described by Robson, namely oblonga and affinis, are determined to have no taxonomic validity. The species polymorpha shows morphological similarities with Pareledone adelieana (Berry, 1917) but differs in relative arm lengths, sucker counts, external colouration and size at maturity. Both species are transferred to the new genus Adelieledone, which is separated from the genus Pareledone s.s. by the transverse ridges in the ligula groove of the hectocotylus, the sharp tip of the lower beak, the enlarged posterior salivary glands, the absence of stylets and by skin sculpture, especially by the presence of two longitudinal integumentary ridges on the dorsal mantle. A new species, Adelieledone piatkowski, is described from the Antarctic Peninsula. Beak morphology can discriminate the genera in predator studies

Rapid selection effects in a short-lived semelparous squid species exposed to exploitation: inferences from the optimisation of life-history functions

The short life span of cephalopods suggests a potential for high sensitivity to the artificial selective effects of human exploitation. To explore the effects of such selection life-history optimisation was applied using data for a semelparous squid, Illex argentinus with a life span of one year. Survival and fecundity functions were combined to generate a life time reproductive potential function. The maximum reproductive potential identified the optimum age for the squid to mature. In a situation of a constant mortality rate the maximum reproductive potential was achieved at an earlier age of maturation as mortality rate increased. The exact age when the optimum maturation occurs is sensitive to the rate of mortality and the form of the assumed growth curve but covers the age range when maturation is known to occur in this species. A more realistic seasonal fishing mortality function produced a more complex fitness curve with a temporally more restricted optimal age of maturity. The selection effects will be stronger in a seasonal fishery suggesting potentially very rapid evolutionary rates. Developing analyses specifically considering frequency-dependence and environmental-feedbacks will be valuable to clarify the potential of squid to show rapid evolutionary responses to selection. Strong selection for early age of maturation could affect the yield from the fishery but more importantly, could also make the migratory strategy, on which the fishery is based, an unviable option, resulting in collapse of the fishery that exploits the migratory component of the species

Production of soma and gonad in maturing male Illex argentinus (Mollusca: Cephalopoda)

Samples of male Illex argentinus were taken from the catch of a Japanese squid jigging vessel on the Patagonian Shelf during March 1986 and an analysis was carried out on the morphometrics of the somatic and reproductive organ systems in relation to maturation. The data show that growth and maturation occurred simultaneously during most of the time that Illex argentinus males were on the feeding grounds over the southern Patagonian Shelf. In a squid of a ‘standard’ mantle length the whole body mass increased relative to mantle length during maturation and this could be attributed to the increase in mass of the reproductive and accessory reproductive organs. During maturation the mantle and digestive gland mass showed no significant change relative to mantle length. The mass of the head increased and the mass of the viscera decreased relative to mantle length. In male Illex argentinus, as in the female, the energy and nutrient resources for maturation are derived from the squid's food and during the course of maturation there is an increasing shift of emphasis from somatic growth to production of gonad and accessory reproductive organs. The proportional investment of body mass in reproductive and accessory reproductive organs predicted for a fully mature male Illex argentinus was less than half that of the female

Cephalopod and groundfish landings: evidence for ecological change in global fisheries?

Cephalopod fisheries are among the few still with some local potential for expansion; in fact, as groundfish landings have declined globally, cephalopod landings have increased. We propose the hypothesis that, although increased cephalopod landings may partly reflect increased market demand, overfishing groundfish stocks has positively affected cephalopod populations. Data from 15 key FAO areas reveal that, with the exception of the north- east Atlantic, cephalopod landings have increased significantly over the last 25 years while groundfish have risen more slowly, remained stable, or declined. In terms of volume, cephalopods have not replaced groundfish. This is hypothesized as owing to the shorter life cycle of cephalopods, and rapid turnover and lower standing stocks than for longer-lived finfish species. Under high fishing pressure, groundfish are probably poor competitors, having less opportunity for spawning and replacement. In West Africa, the Gulf of Thailand and Adriatic there is strong circumstantial evidence that fishing pressure has changed ecological conditions and cephalopod stocks have increased as predatory fish have declined. We recommend that this hypothesis be tested thoroughly in other areas where suitable data exist. Most coastal and shelf cephalopod fisheries are likely to be fully exploited or overexploited, and current annual fluctuations in cephalopod landings are probably largely environmentally-driven

Fine-scale distribution of juvenile cephalopods in the Scotia Sea and adaptive allometry of the brachial crown

The pelagic nekton community was sampled with the RMT 25 opening/closing net and a neuston net at two stations in the Scotia Sea south of the Antarctic Polar Front in the open ocean (Station 1) and on the South Georgia northwestern slope (Station 2). Downward oblique tows were made with the RMT 25 through discrete 200 m layers to 1000 m in daylight and darkness. A total of 119 cephalopods representing nine species were removed from the samples, and mantle and arm lengths were measured to the nearest 0.1 mm. The most abundant species at each station was an undescribed Brachioteuthis sp. (B. ?picta). Galiteuthis glacialis and Alluroteuthis antarcticus were caught at both stations. Histioteuthis eltaninae, Bathyteuthis abyssicola and Psychroteuthis glacialis were caught at Station 1. Mastigoteuthis psychrophila and a Chiroteuthis sp. were caught at Station 2. B. ?picta was present throughout the water column to 1000 m at both stations, with little evidence of ontogenetic descent. There was evidence for ontogenetic descent in G. glacialis. This species was absent from the Antarctic Surface Water (ASW) at Station 1, where it was concentrated in the Circumpolar Deep Water (CDW). At Station 2 it was present throughout the water column to 1000 m. The other species were all caught in the core of the CDW (>400 m). In juvenile B. ?picta, G. glacialis and A. antarcticus, growth of the brachial crown is positively allometric with respect to mantle length. Recent data on biomass spectra in high-latitude pelagic systems show that they are characterised by the presence of peaks of biomass separated by biomass minima. Positive allometric growth in the brachial crown of these antarctic oceanic squid is suggested to have evolved as an adaptation to the peaked, or domed, structure of the pelagic biomass spectrum which must be spanned by these predators as their optimum prey size increases with growth. Interspecific differences in the allometry of tentacle growth are probably related to differences in strategies for stalking and capture of prey