Penguins, fur seals, and fishing: prey requirements and potential competition in the South Shetland Islands, Antarctica

Antarctic and sub-Antarctic seabirds, marine mammals, and human fisheries concentrate their foraging efforts on a single species, Antarctic krill (Euphausiasuperba). Because these predators may have a significant effect on krill abundance, we estimated the energy and prey requirements of Adelie (Pygoscelisadeliae), chinstrap (Pygoscelisantarctica), and gentoo (Pygoscelispapua) penguins and female Antarctic fur seals (Arctocephalusgazella) breeding on the South Shetland Islands, Antarctica and compared these estimates with catch statistics from the Antarctic krill fishery. Published data on field metabolic rate, population size, diet, prey energy content, and metabolic efficiency were used to estimate prey requirements of these breeding, adult, land-based predators and their dependent offspring. Due to their large population size, chinstrap penguins were the most significant krill predators during the period examined, consuming an estimated 7.8 × 10⁸ kg krill, followed by Adelie penguins (3.1 × 10⁷ kg), gentoo penguins (1.2 × 10⁷ kg), and Antarctic fur seals (3.6 × 10⁶ kg). Total consumption of all land-based predators on the South Shetland Islands was estimated at 8.3 × 10⁸ kg krill. The commercial krill fishery harvest in the South Shetland Island region (1.0 × 10⁸ kg) was approximately 12% of this. Commercial harvest coincides seasonally and spatially with peak penguin and fur seal prey demands, and may affect prey availability to penguins and fur seals. This differs from the conclusions of Ichii et al. who asserted that the potential for competition between South Shetland predators and the commercial krill fishery is low. Received: 26 August 1997 / Accepted: 16 December 1997     

External parasite infestation depends on moult-frequency and age in Antarctic krill (<Emphasis Type="Italic">Euphausia superba</Emphasis>)

Levels of infestation by the suctorian Ephelota sp. were determined in Antarctic krill taken in the north-eastern region of the Scotia sea, close to the island of South Georgia. Individuals caught in summer between 2002 and 2004 were measured for body length, eye diameter, moult stage, sex, sexual maturity and number of suctorian parasites. All krill samples were found to contain at least two modal size-classes and the complete range of maturity- and moult stages. Sample analysis for the different characters identified moult stage as an important determinant of infestation by Ephelota sp., with 66% of those about to moult (pre-moult individuals) being infested compared with 0% of post-moult individuals. Multiple Correspondence Analysis also identified a strong link between age and degree of suctorian infestation with large-eyed (and hence old) males having very high numbers of suctorian bodies. Moulting is costly in terms of energy and vulnerability, but it is believed that krill moult at relatively high rates throughout their life to facilitate growth and “shrinkage”. Here, we demonstrate that the control of external parasitism is also a major advantage of moulting at high frequency. The capacity of krill to maintain a high moult rate decreases with age, leading to older krill enduring higher parasitic loads.     

The diet of the Weddell seal <Emphasis Type="Italic">Leptonychotes weddellii</Emphasis> at Laurie Island,South Orkney Islands

The diet of the Weddell seal Leptonychotes weddellii at the South Orkney Islands was investigated by the analysis of 44 and 26 faecal samples collected from the beaches of Laurie Island from May 1999 to January 2000 and from October to December 2001, respectively. The diet was diverse and both pelagic and benthic-demersal organisms were represented in the samples. Fish were the most frequent prey of the samples in both seasons, and fish and krill were the most numerous prey items. Octopods predominated by mass in 1999, whereas krill constituted the bulk of the diet in 2001, a fact that was not observed previously. Among fish, Gobionotothen gibberifrons was largely the species that contributed mostly to the diet, whereas pelagic fish could not be identified in the samples. The results are compared with information from other study areas and discussed in relation to the consumption of krill.     

Interannual variation in the diet of non-breeding male Antarctic fur seals, <Emphasis Type="Italic">Arctocephalus gazella</Emphasis>, at Isla 25 de Mayo/King George Island

The diet of non-breeding male Antarctic fur seals, Arctocephalus gazella, was investigated at Stranger Point, King George Island, through the analysis of scats during three consecutive summer seasons (1996, 1997, 1998). Overall, fish and krill were the most frequent prey occurring, respectively, in an average of 82.9% and 78.8% of samples (n = 131), followed by penguins (22.8%) and cephalopods (17.8%). Myctophids constituted almost 90% of the fish predated, with Electrona antarctica and Gymnoscopelus nicholsi being the most abundant and frequent species consumed. All fish taxa identified were krill feeding species suggesting that seals foraged mainly on a krill and a fish community associated with krill aggregations. However, a seasonal change was observed in the relative proportions of the different prey taxa, with a progressive decrease with time in the occurrence of krill and a concomitant increase of fish, penguins and squid. Possible influence of the strong 1997/98 ENSO event is discussed.     

Zooplankton biomass and abundance of Antarctic krillEuphausia superba DANA in Indian ocean sector of the southern ocean

Zooplankton sampling was carried out during the first six Indian Scientific Expeditions to Antarctica (1981—1987) to estimate krill abundance in the Indian sector of the southern ocean (between 35° to 70° S and 10° to 52° E). This study aims to understand the distribution of biomass of zooplankton, especially the krill, using the data collected by net sampling techniques. Total zooplankton biomass for all the sampling stations ranged from 9 to 684 ml/1000m³ (x: 143.34±138.61 SD; n=150). Biomass data grouped by 5° latitude interval shows the presence of higher biomass (x: 191 ml/1000 m³;n = 31) in the Antarctic divergence region (between 60° to 65° S). EuphausiidEuphausia superba DANA formed a considerable component of biomass and together with eggs and larvae represented over 60% (n = 39) of mean total zooplankton-biomass in the coastal ice region. The values for population density and biomass of adult-size krill varied between 0 to 4320 individuals and 6 to 305 ml/1000 m³, respectively. The highest values were recorded between 62° to 69° S and between 16° to 30° E. A high density of krill larvae was encountered in the shelf region during January 1987 which was related to chlorophyll concentration. However, the values obtained during six consecutive summers showed that values of adult krill biomass at given location was highly variable and, hence, not comparable on inter-annual basis, during the sampling years.     

Distribution,size frequencies and maturity stages of krill,Euphausia superba,in relation to sea-ice in the Northern Weddell Sea

Summary The spring (November) and early summer (December) distribution pattern and demography of Euphausia superba in the seasonally ice covered areas of the north-western Weddell Sea are described. Sampling with a Rectangular Midwater Trawl (RMT) and during SCUBA diving were undertaken in the pack-ice during the EPOS expedition 1988/1989 of RV Polarstern. These data were compared with former cruises during late winter (October) and summer (February). The biomass values of krill (1–27 g/m²) in the water column within the ice covered areas were of the same order of magnitude as earlier acoustic estimates in the ice-edge region of the same area. No significant correlation between percentage ice cover and krill abundance in the water column was found. Cluster analyses of size frequency distributions and maturity stage composition revealed the demography of the animals sampled. Samples obtained by SCUBA and RMT are compatible and results show a geographic and demographic separation of the krill. It is proposed that krill in the northern zone are largely emigrants from the Bellingshausen Sea, while the krill in the southern zone are of eastern Weddell Sea origin. Further studies concentrating on the under-ice distribution of krill are recommended.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation. Publication no 62 of the Alfred-Wegener-Institut für Polar- und Meeresforschung     

Daily activity and minimum food requirements during winter for gentoo penguins (Pygoscelis papua) in the South Shetland Islands, Antarctica

Estimates of daily activity and consequent demand for food during winter are scarce for many polar seabirds, yet essential for assessing constraints on foraging effort, demand for food, and potential competition with local fisheries. We affixed archival temperature tags to gentoo penguins (Pygoscelis papua) from two colonies in the South Shetland Islands to measure the frequency, timing, and duration of foraging trips and to estimate minimum food requirements during winter. Foraging trip frequencies ranged from 0.85 to 1.0 trips day⁻¹ and were positively correlated with day length. Early winter foraging trips more closely matched day length than late winter foraging trips. The data suggest that individuals maximize foraging time during the early winter period, likely to recover body mass following the breeding season and molt. The more attenuated response of foraging trip durations to increasing day length in late winter may be related to differences in local resource availability or individual behaviors prior to the upcoming breeding season. Minimum food requirements also exhibited a seasonal cycle with a mid-winter minimum. On average, minimum food requirements were estimated at 0.70 ± 0.12 kg day⁻¹. Extrapolated to the regional population of gentoo penguins, winter food requirements by gentoo penguins were equivalent to roughly 33% of annual krill catches by commercial fisheries in the South Shetland Island region over the past decade. Current expansion of the gentoo population and the krill fishery in the southern Scotia Sea warrants continued monitoring of gentoo penguins during winter.     

Variability of Euphausia superba populations near Elephant Island and the South Shetlands: 1981 vs. 1984

Summary March 1981 and 1984 Euphausia superba populations were compared using acoustics and net catches near Elephant Island, the South Shetlands, and in the Bransfield Strait. In 1981, krill tended to form large, thick swarms and in 1984, smaller, more dispersed, shallower patches. March body lengths of juvenile-adult krill were 22–59 mm in 1981 and 13–59 mm in 1984. Near Elephant I. in 1981, krill >45 mm were most numerous; in 1984 sizes <45 mm were dominant. In March 1984, the larger (>45 mm) body-size group was prereproductive and occurred from just west of Elephant I. westward into waters north of the South Shetlands; in 1981 the larger krill were postreproductive and more widely distributed in the Elephant I. area. Overall, netted postlarval krill, 1981 vs. 1984, averaged 73 vs. 48 individuals/m², or 54 vs. 16 g/m²; acoustic biomass estimates were 229 vs. 134–201 g/m². Larvae near Elephant I. averaged >2000/m² in 1981 vs. <1/m² in 1984—compatible with respective March reproductive states. Net-type comparisons revealed short-term (15 min to 6h) variability of a similar scale in both MOCNESS and bongo net catches, but bongo abundances averaged greater. Variation in maturity composition across 1981 swarms, patches, and random transects was like variation among the random 1984 tows; spatial distributions were more heterogeneous in 1984. The March 1984 krill of 20–44 mm (Year-2, mode 34 mm) relate to November 1983 krill of 9–30 mm (mode 21 mm), indicating growth averaging 12 mm during the season. Body-lengths and size-frequency modes of Year-2 and combined Years-3,3+ krill from comparable Feb-Mar data collected since 1968 suggest trends between times when (1) Year-2 krill average small and peak reproduction seems to be late in the season and/or weak (1979, 1982–1984), and (2) Year-2 krill are larger, and reproduction is possibly earlier and more successful (1976, 1980, 1981).     

Diet of Cape petrel Daption capense during the post-hatching period at Laurie Island, South Orkney Islands, Antarctica

The diet of Cape petrel Daption capense was investigated at Laurie Island, South Orkney Islands (60°46^′S, 44°42^′W), Antarctica, in the period January–February 1996. Stomach contents of adults and regurgitate of chicks were sampled during the post-hatching period. The analysis showed that during the whole sampling period Antarctic krill and fish represented the predominant preys in terms of frequency of occurrence, forming nearly 35.8% and 64% by mass, respectively. The species Electrona antarctica was the most frequent fish prey. Amphipods were present in lower numbers and cephalopods were detected in the diet, but in a very small proportion. Diet composition in terms of frequency of occurrence, mass and number is compared with results of previous studies. Received: 27 September 1996 / Accepted: 22 February 1997     

The biochemical composition, energy content, and chemical antifeedant defenses of the common Antarctic Peninsular sea stars Granaster nutrix and Neosmilaster georgianus

The sea stars Granaster nutrix and Neosmilaster georgianus are conspicuous members of benthic communities along the Antarctic Peninsula. An analysis of the proximate composition of somatic body components of nonreproductive adults indicates the nutrient storage organs (pyloric caeca) are rich in both protein (60.7 and 60.6% mean dry wt, respectively) and lipid (25.4 and 29.8% mean dry wt, respectively). Body-wall tissues, while containing small inconspicuous skeletal ossicles, are also comprised of significant levels of organic matter (33.5 and 55.7% mean dry wt, respectively), attributable primarily to protein. Both the pyloric caeca and body-wall tissues are relatively rich in energy (mean energy levels=24.8 and 26.5 kJ g⁻¹ dry wt; 8.4 and 14.1 kJ g⁻¹ dry wt, respectively). Despite the availability of these nutrients and energy neither sea star is preyed upon by the sympatric omnivorous sea star Odontaster validus, a common predator of other Antarctic sea stars. Laboratory feeding bioassays indicate that O. validus rejects live intact individuals and body-wall tissues of both sea star species while readily consuming dried krill. Alginate food pellets containing a krill powder and tissue level concentrations of organic methanol extracts of body-wall tissues were also rejected by O. validus. Moreover, the copious mucus released from the body wall of N. georgianus was deterrent in O. validus food pellet bioassays. Thus, both sea stars evidently possess defensive secondary metabolites that defend against predation and are likely to play a role in mediating materials and energy transfer in the Antarctic benthos.     

Distribution and diet of 0-group cod (<Emphasis Type="Italic">Gadus morhua</Emphasis>) and haddock (<Emphasis Type="Italic">Melanogrammus aeglefinus</Emphasis>) in the Barents Sea in relation to food availability and temperature

Distribution of 0-group cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) in August–September 2005 and 2006 was mainly restricted to the Atlantic waters of the western and central areas of the Barents Sea. The main distribution of 0-group fish overlapped largely with areas of high biomass (>7 gm⁻² dry weight) of zooplankton. The copepod Calanus finmarchicus and krill Thysanoessa inermis, which are dominant zooplankton species in both Atlantic and boreal waters of the Barents Sea, were the main prey of 0-group cod and haddock. The main distribution, feeding areas and prey of 0-group cod and haddock overlapped, implying that competition for food may occur between the two species. However, though their diet coincided to a certain degree, haddock seems to prefer smaller and less mobile prey, such as Limacina and appendicularians. As 0-group fish increased in size, there seems to be a shift in diet, from small copepods and towards larger prey such as krill and fish. Overall, a largely pelagic feeding behaviour of 0-group cod and haddock was evident from this study.     

The diet of the Antarctic fur seal Arctocephalus gazella at Harmony Point, Nelson Island, South Shetland Islands

The diet of non-breeding male Antarctic fur seals (Arctocephalus gazella) was investigated at Harmony Point, Nelson Island, South Shetland Islands, by the analysis of 18 and 33 scats collected during February 1996 and 1997 respectively. Overall, fish were the most frequent prey (74.5%) and predominated by mass (54.4%), whereas krill predominated by number (94.2%). This coincides well with the pattern observed in 1997, but in 1996 krill was the most important prey by number and mass (50.2%). The importance of the remaining taxa represented in the samples (octopods, hyperiids and bivalves) was negligible. Among fish, myctophids represented 85.2% of the fish mass, with Gymnoscopelus nicholsi and Electrona antarctica being the main prey. These two species predominated in 1997, whereas the channichthyid Cryodraco antarcticus and the nototheniid Gobionotothen gibberifrons were dominant in 1996. The importance of the myctophids as prey of the Antarctic fur seal is discussed. Received: 7 October 1997 / Accepted: 24 May 1998     

Diet and trophic niche of Antarctic silverfish Pleuragramma antarcticum in the Ross Sea,Antarctica

The diet of Antarctic silverfish Pleuragramma antarcticum was evaluated by examining stomach contents of specimens collected in the Ross Sea (71°–77° S; 165°–180° E) in January to March 2008. Pleuragramma antarcticum (50–236 mm standard length, L_S) and prey items were analysed for stable‐isotopic composition of carbon and nitrogen. According to index of relative importance (I_RI), which incorporates frequency of occurrence, mass and number of prey items, the most important prey items were copepods (81%I_RI over all specimens), predominantly Metridia gerlachei and Paraeuchaeta sp., with krill and fishes having low I_RI (2·2 and 5·6%I_RI overall). According to mass of prey (M) in stomachs, however, fishes (P. antarcticum and myctophids) and krill dominated overall diet (48 and 22%M, respectively), with copepods being a relatively minor constituent of overall diet by mass (9·9%M). Piscivory by P. antarcticum occurred mainly in the extreme south‐west of the region and near the continental slope. Krill identified to species level in P. antarcticum stomachs were predominantly Euphausia superba (14·1%M) with some Euphausia crystallophorias (4·8%M). Both DistLM modelling (PRIMER‐permanova+) on stomach contents (by I_RI) and stepwise generalized linear modelling on stable isotopes showed that L_S and location were significant predictors of P. antarcticum diet. Postlarval P. antarcticum (50–89 mm L_S) consumed exclusively copepods. Juvenile P. antarcticum (90–151 mm L_S) consumed predominantly krill and copepods by mass (46 and 30%M, respectively). Small adult P. antarcticum (152–178 mm L_S) consumed krill, fishes and copepods (37, 36 and 15%M, respectively). Large adult P. antarcticum (179–236 mm L_S) consumed predominantly fishes and krill (55 and 17%M, respectively), especially in the north (near the Ross Sea slope) and in the SW Ross Sea. Amphipods were occasionally important prey items for P. antarcticum (western Ross Sea, 39%M). General concordance between stomach contents and trophic level of P. antarcticum and prey based on δ¹⁵N was demonstrated. Pleuragramma antarcticum trophic level was estimated as 3·7 (postlarval fish) and 4·1 (fish aged 3+ years).     

Food and daily food consumption of southern minke whales in the Antarctic

Summary The stomach contents of 273 southern minke whales (Balaenoptera acutorostrata) taken in the region 55°S to the ice-edge and between 105°E and 115°E by a Japanese survey during 1987/88 were examined. The minke whales' dominant feeding ground coincided with a distinctive hydrographic front in the vicinity of the ice-edge at the mouth of Vincennes Bay. Krill (Euphausia superba) were the dominant food species comprising 100% and 94% by weight of stomach contents in the ice-edge and offshore zones, respectively. In the offshore zone, minke whales tend to feed on E. superba rather than Thysanoessa macrura, which is found more frequently than the former in net samples. Total food consumption by minke whales per day was estimated to be 1170 t (22.1 kg/km²) and 596 t (2.0 kg/km²) in the ice-edge and offshore zones, respectively. Feeding activity peaked in the early morning in the ice-edge zone, whereas it occurred irregularly throughout the day in the offshore zone. Two size modes of krill (25–28 mm in body length (1 year-old) and 41–48 mm (3–4 year-old)) dominated the diet. Although the former was numerically more abundant, the latter dominated the diet by weight, suggesting that larger krill are more important food for minke whales. Observed spatial pattern of krill populations in the study region suggests that movement of the subsurface cold water mass tended to carry krill offshore from the ice-edge.The earlier version of this paper was submitted to the 42nd Meeting of the Scientific Committee of International Whaling Commission as SC/42/SHM; 34.     

Phytoplankton growth and krill grazing during spring in the Bransfield Strait,Antarctica — Implications from sediment trap collections

Summary Phytoplankton primary production, biomass, species composition and sedimentation of organic matter (using a moored and a free drifting sediment trap) were measured in eastern Bransfield Strait during spring 1983. Biomass and primary production increased from low levels in late November (1 mgChla m^-3 and 400 mgC m^-2 d^-1) to bloom levels by the end of December (5 mgChla m^-3 and 1000 mgC m^-2 d^-1). The moored trap was deployed at 323 m depth for 22.5 days, and collected 2968 mgC and 67.6 mg chlorophyll a and derivatives per m² (132 and 3.0 mg m^-2 d^-1), of which 90% was in the form of krill faeces. These figures are regarded as egestion of krill, and using ingestion: egestion ratios from the literature, grazing loss of phytoplankton by krill was estimated at 45% of the primary production during a period of 3 weeks. Large-scale surveys of phytoplankton standing stock indicate that the build-up of blooms during spring is apparently not controlled by krill grazing. It is therefore suggested that the intense grazing that must have occurred over the trap during the period of deployment was only of local importance.     

Challenges using stable isotopes for estimating trophic levels in marine amphipods

In marine food web studies, stable isotopes of nitrogen (δ¹⁵N) and carbon (δ¹³C) are widely used to estimate organisms’ trophic levels (TL) and carbon sources, respectively. For smaller organisms, whole specimens are commonly analyzed. However, this “bulk method” involves several pitfalls since different tissues may fractionate stable isotopes differently. We compared the δ¹⁵N and δ¹³C values of exoskeleton versus soft tissue, in relation to whole specimens, of three common Arctic amphipods in Svalbard waters: the benthic Anonyx nugax, the sympagic (ice-associated) Gammarus wilkitzkii and the pelagic Themisto libellula. The δ¹⁵N values of the exoskeletons were significantly lower than those of the soft tissues for A. nugax (10.5 ± 0.7‰ vs. 15.7 ± 0.7‰), G. wilkitzkii (3.3 ± 0.3‰ vs. 8.3 ± 0.4‰) and T. libellula (8.6 ± 0.3‰ vs.10.8 ± 0.3‰). The differences in δ¹³C values between exoskeletons and soft tissues were insignificant, except for A. nugax (−21.2 ± 0.2‰ vs. −20.3 ± 0.2‰, respectively). The δ¹⁵N values of whole organisms were between those of the exoskeletons and the soft tissues, being similarly enriched in ¹⁵N as the exoskeletons (except G. wilkitzkii) and depleted in ¹⁵N by 1.2–3.7‰ compared to the soft tissues. The δ¹⁵N-derived TLs of the soft tissues agreed best with the known feeding preferences of the three amphipods, which suggest a potential underestimation of 0.5–1.0 TL when stable isotope analyses are performed on whole crustaceans with thick exoskeletons. The insignificant or small differences in δ¹³C values among exoskeletons, soft tissues and whole specimens, however, suggest low probability for misinterpretations of crustaceans’ primary carbon source in marine ecosystems with distinctly different δ¹³C-carbon sources.     

Diet of the Antarctic starry skate Amblyraja georgiana (Rajidae, Chondrichthyes) at South Georgia (Southern Ocean)

Stomach contents were identified from 206 Antarctic starry skate (Amblyraja georgiana) that were collected during three groundfish surveys (September 2007, April 2008 and January 2009) at South Georgia, Southern Ocean. The diet of A. georgiana varied with skate size and between years. Preferred prey included fish (particularly for larger individuals) and Antarctic krill, Euphausia superba, as well as amphipods, polychaetes and other benthic fauna. The skate A. georgiana appears to be an opportunistic predator, and the clear presence of Antarctic krill in this demersal predator’s diet may indicate a benthic habit of this euphausiid species, which has hitherto mainly been considered as occupying a purely pelagic niche.     

Diet of two icefish species from the South Shetland Islands and Elephant Island,<Emphasis Type="Italic"> Champsocephalus gunnari</Emphasis> and<Emphasis Type="Italic"> Chaenocephalus aceratus</Emphasis>

The summer diet of two species of icefishes (Channichthyidae) from the South Shetland Islands and Elephant Island, Champsocephalus gunnari and Chaenocephalus aceratus, was investigated from 2001 to 2003. Champsocephalus gunnari fed almost exclusively on krill (Euphausia superba) in all years. The importance of other taxa (Themisto gaudichaudii, mysids, myctophids) in the diet was negligible. The average feeding rate of Champsocephalus gunnari inferred from an exponential gastric evacuation model was between 1.0 and 1.5% body weight per day. Most of the stomachs of Chaenocephalus aceratus were empty. Stomachs with food contained mainly krill, mysids and fish. Among the fish taken, locally abundant species formed the bulk of the diet: Gobionotothen gibberifrons in 2001, Lepidonotothen larseni and Champsocephalus gunnari in 2002 and L. larseni in 2003. An ontogenetic shift in feeding preference of Chaenocephalus aceratus was observed: fish smaller than 30 cm fed on krill and mysids, while larger animals relied primarily on fish.     

Occurrence of cyclopoid copepods and faecal material in the Halley Bay region,Antarctica, during January–February 1991

Faecal material and cyclopoid copepods were collected during the expedition ANT IX/3, in the Halley Bay area (Weddell Sea, Antarctica), between January and February 1991. Faecal material comprised pellets produced by krill, copepods, ostracods and appendicularians. Cyclopoid copepods were represented by two genera, Oithona and Oncaea. In the Halley Bay area, higher concentrations of krill faecal material (420.9 mm³ m^–2) and chl.-a (39.3 mg m^–2) were found within the upper 200 m of the water column of the polynya than in ice-covered open-ocean areas (58.2 mm³m^–2 and 25.5 mg m^–2, respectively). At an ice-drift station, high concentrations of krill faecal strings under fest-ice were found. In addition, similarities between diatom assemblages in the pack-ice algae and krill faecal strings contents suggest an active utilization of ice-algae by krill populations. Sedimented material collected at 50 m depth by a sediment trap was dominated by krill faecal strings. Contents of small oval pellets (of probable cyclopoid copepod origin) resemble those of krill faecal pellets suggesting that coprophagy was involved. This suggestion is supported by: (1) The small quantity of food particles (other than krill faecal matter) available in the water column (< 0.3 g chl.-al^–1). (2) The negative in situ correlation between krill faecal strings and cyclopoid copepods. (3) The structure of cyclopoid copepod buccal appendages, which are more adapted for raptorial feeding.