Gonatus Antarcticus Research Articles

Trophic structure of Southern Ocean squid: a cross-basin analysis of stable isotopes in archived beaks from predator stomachs

Cephalopods are an important component of Southern Ocean food webs, but aspects of their trophic ecology remain unresolved. Here, we used archived squid (order Teuthida) beaks, collected from stomach contents of predators at Macquarie and Kerguelen Islands, to investigate the trophic structure within an assemblage of pelagic squids (Alluroteuthis antarcticus, Filippovia knipovitchi, Gonatus antarcticus, Histioteuthis eltaninae, Martialia hyadesi and Brachioteuthis linkovskyi). We combined bulk nitrogen stable isotopes (δ15Nbulk) with compound-specific isotope analysis of amino acids (CSIA-AA) to estimate the trophic position (TP) of species and to assess isotopic relationships with body size at the species, community, and ocean basin levels. We observed significantly higher mean δ15Nbulk values for species at the Kerguelen Islands compared to conspecifics at Macquarie Island. This result was explained by regional variability in δ15N values of phenylalanine (δ15NPhe), suggesting that predator species were accessing different isotopic baselines at each region. This may highlight the different foraging strategies of both species. The overlap in species TP estimates from CSIA-AA (TPCSIA) between the 2 communities (Macquarie Island TPCSIA min: 2.3, max: 5.3; Kerguelen Islands TPCSIA min: 2.7, max: 5.3) indicated a similar trophic structure at both locations. We note unrealistically low TPCSIA for some species, which we attribute to uncertainty of trophic discrimination factors. TP estimates suggested that squid encompass 3 trophic levels from mid-trophic levels to higher predators. We did not find strong or consistent relationships between TP and body size at either the species- or community-level. One of the largest squid species, M. hyadesi, occupied the lowest TP in both communities. These new insights into the trophic structure of the Southern Ocean squid community have important implications for the future representation of pelagic squids in ecosystem models.

Long-term changes in habitat and trophic level of Southern Ocean squid in relation to environmental conditions

Long-term studies of pelagic nekton in the Southern Ocean and their responses to ongoing environmental change are rare. Using stable isotope ratios measured in squid beaks recovered from diet samples of wandering albatrosses Diomedea exulans, we assessed decadal variation (from 1976 to 2016) in the habitat (δ13C) and trophic level (δ15N) of five important Southern Ocean squid species in relation to indices of environmental conditions—Southern Oscillation Index (SOI) and Southern Annular Mode (SAM). Based on δ13C values, corrected for the Suess effect, habitat had changed over the last 50 years for Taonius sp. B (Voss), Gonatus antarcticus, Galiteuthis glacialis and Histioteuthis atlantica but not Moroteuthopsis longimana. By comparison, mean δ15N values were similar across decades for all five species, suggesting minimal changes in trophic levels. Both SAM and SOI have increased in strength and frequency over the study period but, of the five species, only in Taonius sp. B (Voss) did these indices correlate with, δ13C and δ15N values, indicating direct relationships between environmental conditions, habitat and trophic level. The five cephalopod species therefore changed their habitats with changing environmental conditions over the last 50 years but maintained similar trophic levels. Hence, cephalopods are likely to remain important prey for top predators in Southern Ocean food webs, despite ongoing climate change.

Mercury levels in Southern Ocean squid: Variability over the last decade

The concentrations of total and proportions of organic mercury were measured in tissues of 355 individuals of 8 species of Southern Ocean squid (Alluroteuthis antarcticus, Bathyteuthis abyssicola, Filippovia knipovitchi, Galiteuthis glacialis, Gonatus antarcticus, Kondakovia longimana, Psychroteuthis glacialis and Slosarczykovia circumantarctica). Squid were caught around South Georgia (Scotia Sea) during 5 cruises, between the austral summers of 2006/07 to 2016/17 to evaluate temporal changes in bioaccumulation and tissue partitioning. Total mercury concentrations varied between 4 ng g−1 and 804 ng g−1 among all tissues. Net accumulation of mercury in muscle with size was observed in A. antarcticus, B. abyssicola and P. glacialis, but no relationship was found for S. circumantarctica and lower concentrations were observed in larger individuals of G. glacialis. Muscle tissues had the highest mercury concentrations in the majority of species, except for F. knipovitchi for which the digestive gland contained highest concentrations. In terms of the percentage of organic mercury in the tissues, muscle always contained the highest values (67%–97%), followed by the digestive gland (22%–38%). Lowest organic mercury percentages were found consistently in the gills (9%–19%), suggesting only low levels of incorporation through the dissolved pathway and/or a limited redistribution of dietary organic mercury towards this tissue. Overall, results are indicative of a decreasing trend of mercury concentrations in the majority of analysed species over the last decade. As cephalopods are an important Southern Ocean trophic link between primary consumers and top predators, these changes suggest decreasing mercury levels in lower trophic levels and an alleviation of the mercury burden on higher predators that consume squid.

Two new findings of large maturing and spent females of deep sea squid Gonatus antarcticus on the continental slope in the south-west Atlantic

A spent Gonatus antarcticus female (mantle length 340 mm) was caught in Falkland Islands waters by a fishing vessel in November 2010. Squid genus Gonatus spawn at depths of >2000 m and findings of such females are rare all over the world. It is the third capture of a mature female of this species, and the shallowest capture for adult squids of the genus. Another G. antarcticus, an immature female, of the record size of 470 mm (mantle length) was caught in June 2011 in Falkland Islands waters, also by a pelagic fishing vessel.

Vestigial phragmocone in the gladius points to a deepwater origin of squid (Mollusca: Cephalopoda)

The microstructure of the gladius cone was investigated in six species of nektonic squid: shallow-water Loligo gahi (Loliginidae), pelagic eurybathic Illex argentinus, Todarodes pacificus, Dosidicus gigas (Ommastrephidae), and deepwater Onykia ingens (Onychoteuthidae) and Gonatus antarcticus (Gonatidae) using state-of-the-art microscopy. Apart from L. gahi, all other species had septa-like layers in the gladius cone, which for the first time were investigated in detail and compared with those in extinct Cretaceous belemnites Hibolithes sp. and Pachyteuthis sp., and spirulid Cyrtobelus sp. It was found that the organic layers of the gladius cone in recent squid can be homologized with the organic components of the shell in fossil phragmocone-bearing coleoids. The septa-like layers in modern gladius cones therefore represent a vestigial phragmocone composed of organic septal rudiments of the ancestral phragmocone that has lost the siphuncle and gas-filled chambers. The well-developed rostrum in onychoteuthids and small rostrum of the gladius in ommastrephids and gonatids can be seen as homologous with the belemnoid rostrum, which may indicate a close phylogenetic relationship between belemnites and at least some squid. Possible evolutionary pathways of the reduction of the functional phragmocone in squid ancestors are discussed. Several features such as the loss of shell calcification, deep water speciation, and the structure of the equilibrium organ point to a deep-water origin of squids.

Fatty acid signatures of stomach contents reflect inter- and intra-annual changes in diet of a small pelagic seabird, the Thin-billed prion Pachyptila belcheri

In diet analyses of seabirds, fatty acid signatures (FAS) can be used to overcome biases due to differential digestion of prey and enable the analysis of very digested diet samples. We applied FAS analysis to stomach contents of a small sub-Antarctic seabird, the Thin-billed Prion Pachyptila belcheri, which feeds mainly on squid during incubation and on crustacea during chick rearing. This seasonal dietary switch of Thin-billed prions was reflected in differences in FAS in regurgitates, as were inter-annual differences in diet composition. A discriminant function analysis correctly classified 93.4% of cases with respect to year (2006–2008) and stage of the breeding cycle (incubation versus chick rearing). The dominant types of crustacea in the diet of Thin-billed prions (amphipods Themisto gaudichaudii, euphausiids, decapods Munida gregaria, and calanoid copepods) were distinguished well by characteristic FAS patterns. However, the FAS of the two main types of prey by volume, amphipods T. gaudichaudii and squid Gonatus antarcticus, were similar to each other. Although FAS were successfully applied in the analysis of prey in stomach contents of prions, FAS of some prey species were similar and may not be distinguishable from each other if used in quantitative diet analyses.

Cephalopods caught in the outer Patagonian shelf and its upper and medium slope in relation to the main oceanographic features

Ninety cephalopod specimens were collected in 71 of the 132 hauls (54%) during the bottom trawl survey ATLANTIS 2009 undertaken between 24 February and 1 April 2009. The surveyed area was the zone between parallels 44° and 48° South, east of the Argentinean Exclusive Economic Zone down to the 1500 m depth contour on the high seas of the Southwest Atlantic. The collection was composed of 16 species of squids and 5 of octopods. The best represented groups were Histioteuthidae (5 species) and Octopodidae (5). The most abundant species were Gonatus antarcticus (25.5%), Histioteuthis atlantica (11.1%), and Muusoctopus eureka (8.9%), which were also the most widely encountered. The geographic and/or bathymetric distribution ranges of 9 species are extended, and this is the first record of Galiteuthis glacialis outside circumpolar Antarctic waters. Our data show that several species, mainly of octopuses, penetrate the area studied as the plume of cold sub-Antarctic waters is pushed far into the Southwestern Atlantic by the Falkland (Malvinas) Current.

Convergence in life-history traits in migratory deep-water squid and fish

AbstractArkhipkin, A. I., and Laptikhovsky, V. V. 2010. Convergence in life-history traits in migratory deep-water squid and fish. – ICES Journal of Marine Science, 67: 1444–1451. The life-history traits of two species of nektonic squid, Onykia ingens and Gonatus antarcticus, and Patagonian toothfish Dissostichus eleginoides, all from the Southwest Atlantic, are reviewed to reveal the extent to which their life cycles have converged. All three follow similar ontogenetic migration, with spawning and egg development in meso-bathypelagic water over the continental slope. Larvae and small juveniles ascend to epipelagic water to feed and grow near the slope. Juveniles and immature adults migrate to the shelf and use it as their feeding grounds. After this period of fast growth on the shelf, the adults descend back to deep water to spawn. The potential advantages that such a life cycle gives to migratory deep-water animals over obligate bathypelagic and benthic fauna are discussed. The most likely cause of ontogenetic migration of juvenile deep-water organisms to the shelf, with the resulting fast growth, is to increase individual fecundity during the adult deep-water phase. Escape from predation and resource utilization at the next trophic level are also examined, but found to be less plausible explanations. Larger, mature animals have higher fecundity, bigger eggs, and larger, better-developed hatchlings, all of which enhance the survival rates of the species at the early stages of their ontogenesis.

Squid as a resource shared by fish and humans on the Falkland Islands’ shelf

Nektonic squids are the dominant group in the Falklands Islands’ fishery representing >75% of the total annual catch. Among these squids, the benthopelagic Loligo gahi is an important link between zooplankton and fish in the shelf food web. It is preyed upon by diverse and numerous demersal and benthopelagic fishes, penguins and marine mammals, and is harvested by fishermen. Pelagic squids, Illex argentinus, Onykia ingens, and Gonatus antarcticus though seasonally very abundant, are scarce in fish diet because of the absence of specialised pelagic predators. This ecological niche is shared between humans (targeting Illex) and penguins (targeting Onykia and Gonatus). Martialia hyadesi though was abundant in some years in the past, it has now virtually disappeared from the shelf ecosystem. The biomass produced by L. gahi remains in the Falkland waters, whereas that of pelagic squid is transported out of the shelf either to the northern Patagonian slope ( I. argentinus) or to deeper waters around the islands ( O. ingens and G. antarcticus). Generally squids occupy the ecological niche of epipelagic fish on the Falkland shelf and slope.

Shearwater diet during migration along the coast of Rio Grande do Sul, Brazil

The coastline of the state of Rio Grande do Sul (Brazil) is used annually as a migratory route by a number of seabird species. Thirteen surveys were carried out between July 1997 and July 1998 to obtain information on the diet of Puffinus gravis, Puffinus griseus, and Puffinus puffinus along the coast of Rio Grande do Sul. Sampling efforts focused on dead beach-cast specimens. One hundred twenty-one stomach content analyses were performed on P. gravis from a total of 238 specimens; 17 stomach content analyses were performed on P. griseus from a total of 54 specimens; and 25 stomach content analyses were performed on 25 P. puffinus from a total of 61 dead specimens. Cephalopods were the main prey found in the stomachs of the three species and were present in 96% of the P. gravis stomachs. The following cephalopods were observed: Ommastrephidae, Gonatus antarcticus, Gonatus sp., Lycoteuthis lorigera, Lycoteuthis sp., Histioteuthis sp., Cycloteuthis sp., Loligo plei, Loligo sanpaulensis, Sepiidae, and Argonauta nodosa. The latter was the most abundant species in the three species of Puffinus. The following fish were identified from otoliths: Porichthys porosissimus, Ctenosciaena gracilicirrhus, Paralonchurus brasiliensis, Cynoscion guatucupa, and Trichiurus lepturus. There was also a high incidence of synthetic materials such as plastic, polyethylene and rubber.

The trophic link between squid and the emperor penguin Aptenodytes forsteri at Pointe Géologie, Antarctica

Cephalopod beaks retrieved from stomachs of dead emperor penguin chicks at Pointe Geologie, Terre Adelie, provide information on taxonomic and size composition of the penguin’s squid diet, on the trophic range of the squid species preyed upon and on the fractional trophic impact of the penguin on the whole food web. Emperor penguins prey upon four squid species (Psychroteuthis glacialis, Kondakovia longimana, Gonatus antarcticus, Alluroteuthis antarcticus) and do not take squid larger than 480 mm mantle length. Larger squid live either below the penguin’s diving range or are beyond its handling capacity. Nitrogen stable isotope ratios indicate that squids cover a range of about two trophic levels (2.5–8‰ δ15N). The impact of the emperor penguin, however, concentrates on the upper part of this range, about 68% of its squid prey being >6‰ δ15N. The principal components of the emperor’s diet, fish, krill and squid, differ distinctly in average trophic level. Consequently the trophic position of the emperor penguin changes accordingly with diet composition and may differ by almost one trophic level between different emperor penguin colonies.

Reproductive biology in two species of deep-sea squids

Deep-sea squids, Moroteuthis ingens and Gonatus antarcticus, were collected in the slope waters off the Falkland Islands and their reproductive systems preserved and investigated onshore. Changes in oocyte length-frequencies at maturation and spawning, and their fecundity were studied. These squids, as well as many other species, are characterised by a synchronous oocyte growth and ovulation. Oviducts are not used for ripe egg accumulation and consequently the universal scale of Lipinski (1979) cannot be applied to assign female maturity. M. ingens spawns near the bottom; its fecundity is 168-297 thousand eggs. Maximum egg size is 1.8-2.7 mm. G. antarcticus spawns midwater; its fecundity is 10-25 thousand eggs. Egg size is 3.2-3.3 mm. In M. ingens spawning takes place in the austral autumn and winter, in G. antarcticus-in austral winter. Our data and the literature data show that the so-called "synchronous ovulation" probably occurs in all deepwater squids. This pattern is very rare among fish, but is quite common among benthic octopods that brood their egg masses.

Trophic relationships of white-chinned petrels from Crozet Islands: combined stomach oil and conventional dietary analyses

The diet of white-chinned petrels Procellaria aequinoctialis breeding at the Crozet Archipelago (southern Indian Ocean) was studied using two complementary methods: lipid analysis of stomach oils as trophic markers together with the conventional dietary approach (i.e., stomach content analysis). Objectives were (1) to investigate the adult diet when they feed for themselves by analyzing stomach oil lipids, and (2) to compare the lipid signature of chick and adult oils. Stomach oils mainly consisted of triacylglycerols (TAG), diacylglycerol-ethers (DAGE) and wax esters (WE) (66, 14 and 11%, respectively). The dietary origin of TAG and WE was evaluated by linear discriminant analyses with fatty acid and fatty alcohol fractions. Analyses evidenced that stomach oils did not originate from Antarctic krill, but instead from myctophid fish, thus demonstrating the importance of mesopelagic fish in the nutrition of adult petrels. This result was consistent with the identification of digested remains of myctophids recovered from adult stomach contents after long foraging trips. Large amounts of a rare lipid class, DAGE (up to 76% of total lipids), were identified in two stomach oils, together with fresh remains of the squid Gonatus antarcticus (99% by mass), suggesting that DAGE could have the potential to be trophic markers of cephalopods. Moreover, six oils probably originated from Patagonian toothfish, thus confirming strong interactions between white-chinned petrels and fisheries. Comparison between chick and adult stomach oils indicated no major differences in their biochemical composition suggesting an identical dietary origin of oils, mainly myctophids. Both adult and chick oils can therefore be used to determine the feeding ecology of adult birds when they feed far away from their breeding grounds. Finally, food analysis of chick samples and adult samples collected after short and long trips indicated different foraging grounds during the two kinds of trips, and also between long trips performed in subtropical and Antarctic waters.

Interannual variations in cephalopod consumption by albatrosses at South Georgia: implications for future commercial exploitation of cephalopods

Assessing the consumption of prey by predators in the marine environment is key to fisheries assessment and management. Although environmental and ecological variations can affect the consumption of certain prey by albatrosses interannually, this issue has not been addressed to date. In the present study, the interannual consumption of cephalopods by grey-headed and black-browed albatrosses was assessed while breeding at South Georgia between 1996 and 2000, by comparing consumption estimates from a reparameterised version of the South Georgia Seabird Impact Assessment (SGSIA) model. The reparameterised model showed that there are considerable interannual variations in cephalopod consumption in both albatross species, with the highest consumption occurring in 1996 (5787 tonnes; for black-browed albatrosses) and 1997 (11 627 tonnes; for grey-headed albatrosses), and the lowest in 2000 (2309 tonnes and 772 tonnes for grey-headed and black-browed albatrosses respectively). These interannual variations were linked to oceanographic conditions and changes in cephalopod abundance/availability to predators. The cephalopod species with the most commercial potential (Martialia hyadesi, Kondakovia longimana, Moroteuthis knipovitchi and Gonatus antarcticus) also showed considerable differences in their consumption by predators. Owing to the importance of these squid species in the diet of albatrosses, precautionary measures for future commercial exploitation are suggested.

Inter-annual variation in the diet of female southern rockhopper penguin (Eudyptes chrysocome chrysocome) at Tierra del Fuego

Inter-annual variation in the diet of female southern rockhopper penguins (Eudyptes chrysocome chrysocome) at Staten Island was studied during the early chick-rearing period to investigate the components of the diet and highlight some points of the possible food web in the study area. Gregarious crustaceans, small juveniles of squid and octopus, fish larvae and juvenile fish dominated the diet. There was a high degree of variability in the relative contribution of the different prey taxa during the three seasons studied. Overall, crustaceans were by far the most abundant in terms of number. Cephalopods contributed less to numbers, while fish was the least represented of the prey item in 2 years. Inter-annual variation in the proportion of prey items consumed was apparent only for some prey species: Thysanoessa gregaria, Gonatus antarcticus, Themisto gaudichaudii, Harpagifer bispinis and Salilota australis. These data suggest variability in the prey resources at sea during the study period and a subsequent opportunism of this penguin species to exploit what is differentially available. In terms of the food web in the area, we suggest an apparent relationship in the availability between T. gaudichaudii and G. antarcticus, and between T. gaudichaudii and H bispinnis. These relationships emphasise the importance of understanding food web interactions, especially those involving multiple trophic levels, when determining the role of upper-trophic level predators in marine systems.

A comparative study of the cephalopod prey of Patagonian toothfish (Dissostichus eleginoides) and southern elephant seals (Mirounga leonina) near Macquarie Island

Within the Southern Ocean, Patagonian toothfish (Dissostichus eleginoides Smitt) and southern elephant seals (Mirounga leonina Linnaeus) forage mainly on fish and cephalopods. From what is known of their diets, the proportion of fish is greatest in toothfish diet. When foraging at-sea for squid, elephant seals and toothfish most often co-occur over continental shelves and submarine plateaux surrounding sub-Antarctic land masses within the Southern Ocean. I used traditional (non-molecular) techniques to compare the squid diet of these two predators. Of the 21 squid species identified, 10 were common to the diets of both predators. One species, Gonatus antarcticus, dominated (61%) the biomass of squid consumed by toothfish, but was of little importance to the elephant seals (2.3%). By contrast, Martialia hyadesi was the most important single species to the elephant seals’ diet (29%), but it contributed 1% to the toothfish diet. Onychoteuthids (Kondakovia longimana, Moroteuthis ingens and Morotenthis knipovitchi) were important to both predators’ diets. The median sizes of five cephalopod species (Slosarczykovia circumantarctica, Galiteuthis glacialis, Gonatus antarcticus, Moroteuthis ingens and Moroteuthis knipovitchi) which were common to both the seal and toothfish diets, were significantly larger in the toothfish stomachs than in the elephant-seal stomachs. Percent similarity indices for the squids that overlapped both diets were in some cases as high as 100%. However, after between-species differences in prey size consumption were accounted for, the similarities fell to between 20 and 50%. These results indicate that the strength of the trophic interaction between the seals and the fish might be weaker than previously thought. The consumption of significantly different-sized squid can also be used to suggest spatial (vertical) foraging separation of these two predators because there is evidence for ontogenetic change in the size of squid species with depth; older, and thus larger, squids live deeper than smaller individuals of the same species.

Summer diet of king penguins (Aptenodytes patagonicus) at the Falkland Islands, southern Atlantic Ocean

The diet of king penguins (Aptenodytes patagonicus) brooding chicks was investigated during February 2001 at the Falkland Islands, where a small but increasing population is located at the limit of the breeding range of this species. Fish was the most important food source by number (98.0%) and reconstituted mass (97.8%), squids accounting for the remainder. Myctophid fishes represented the main part of the diet (97.7% by number and 96.6% by reconstituted mass), Protomyctophum choriodon being by far the main prey item (84.2% and 88.1%, respectively). Four other myctophids and one squid species each contributed to more than 1% of the diet by number: Krefftichthys anderssoni (4.8%), Electrona carlsbergi (4.6%), Gymnoscopelus nicholsi (2.2%) and Protomyctophum tenisoni (1.8%), together with small juveniles of Gonatus antarcticus (1.8%). Twelve squid species were identified from accumulated lower beaks, including the ommastrephid Martialia hyadesi (48.3% by number), the onychoteuthids Moroteuthis ingens (15.6%), Kondakovia longimana (10.5%) and Moroteuthis knipovitchi (7.3%), and Gonatus antarcticus (9.2%). The stable-carbon and stable-nitrogen isotopic composition of chick food and adult blood differed in a way that suggests that, during the same trip, adult birds fed for themselves in distant foraging grounds, and fed for their chicks on their way back to the colony. The study emphasizes that king penguins are specialist myctophid eaters throughout their breeding range in summer, and highlights the importance of Protomyctophum choriodon as a link between zooplankton and top predators in the pelagic ecosystem of the southwestern Atlantic Ocean.

Lipid and fatty acid composition of the mantle and digestive gland of four Southern Ocean squid species: implications for food-web studies

Lipid content, lipid class and fatty acid composition of four Southern Ocean cephalopod species – the myopsid Sepioteuthis australis and three oegopsids, Gonatus antarcticus, Moroteuthis robsoni and Todarodes spp. – were analysed. The lipid content of the digestive gland was consistently greater than that of the mantle, and was an order of magnitude greater in oegopsid species. The lipid class and fatty acid composition of the mantle and digestive gland also differed markedly in each species. Digestive gland lipid is likely to be of dietary origin, and large amounts of lipid in the digestive gland of oegopsids may accumulate over time. Thus the digestive gland is a rich source of fatty acid dietary tracers and may provide a history of dietary intake. However, the absolute amount of dietary lipid in the digestive gland of oegopsid species exceeds the absolute lipid content of mantle tissue. Therefore the overall lipid “signature” of an oegopsid may more closely resemble its prey species rather than its mantle tissue. When lipid techniques are used in dietary analysis of teuthophagous predators, squid may not be represented by a unique signature in analyses and their importance in the diets of predators may be underestimated.

Humans and the Southern Elephant Seal Mirounga leonina

Southern elephant seal (Mirounga leonina) populations appear remarkably unaffected by interactions with humans. They are very tolerant of close human presence whilst they are ashore for pupping, mating and moulting. Their behaviour in close proximity to helicopter operations suggests disturbance of moulting male M. leonina is minimal. There is no evidence that M. leonina have been affected by persistent organic pollutants; and few M. leonina have been reported as having been injured or killed by interactions with fishery gear. The number of prey species common to their diet and commercial fisheries in the Southern Ocean are few; but one commercial squid species, Martialia hyadesi, accounted for as much as 94% of the biomass consumed by M. leonina. Two harvested commercial squid species (Mar. hyadesi and Todarodes filippovae) were found in the stomachs of M. leonina; and some other squid species (Alluroteuthis antarcticus, Brachioteuthis spp., Gonatus antarcticus, Histeoteuthis spp., Kondokovia longimana, Moroteuthis ingens, Mor. knipovitchi, Pholidoteuthis boschmani and Psychroteuthis glacialis) have potential as commercial catch too. There is cause for concern if a future directed fishery for any of these species escalates or the by-catch of Mar. hyadesi and T. filippovae in the Illex and Nototodarus fisheries increase. There is also concern if fin-fish fisheries expand and take more of those species already taken by both M. leonina and fisheries. These species are benthic (Notothenia squamifrons), benthopelagic (Dissostichus eleginoides and Champsocephalus gunnari) and, perhaps most importantly, the pelagic myctophid species (e.g., Electrona carlsbergi).

Cephalopod prey of king penguins ( Aptenodytes patagonicus) breeding at Volunteer Beach, Falkland Islands, during austral winter 1996

The beaks of 10 cephalopod species were found in the diet of foraging and moulting king penguins ( Aptenodytes patagonicus) from a breeding colony at Volunteer Beach, Falkland Islands during austral winter (September/October 1996). A total of 486 lower cephalopod beaks were collected , identified and measured (LRL: lower rostral length). Six cephalopod families occurred in the penguins’ diet with Onychoteuthidae being the most abundant (256 lower beaks) and represented by Moroteuthis ingens (168; LRL range 2.1–6.8 mm), Moroteuthis knipovitchi (79; LRL range 1.9–5.5 mm), and Kondakovia longimana (9; LRL range 2.1–7.4 mm). Other families were Ommastrephidae (135) with Martialia hyadesi (127; LRL range 2.6–8.7 mm), Illex argentinus (6; LRL range 5.0–6.0 mm), and Ommastrephes bartrami (2; LRL range 7.9–8.8 mm); Loliginidae with Loligo gahi (60; LRL range 0.8–2.1 mm); Gonatidae with Gonatus antarcticus (28; LRL range 1.3–3.3 mm); Neoteuthidae with Alluroteuthis antarcticus (4; LRL range 2.4–3.9 mm), and Histioteuthidae with Histioteuthis eltaninae (3; LRL range 3.3–3.4 mm). Allometric equations were used to relate lower rostral beak length with cephalopod body size and mass. M. ingens was the dominating cephalopod prey in terms of numbers ( n=168), whereas M. hyadesi was most important in terms of biomass (64 682 g). The present study provides first information on the cephalopod prey of Falkland Islands king penguins. The data suggest that penguins take squid at coastal islands slope regions as well as in oceanic waters which demonstrates their ability to forage in a wide geographical area and to alternate between specific foraging sites. Possible competition with the commercial squid fishery off the Falkland Islands is discussed.