Fish in the diet of the Antarctic shag Phalacrocorax bransfieldensis at Laurie Island, South Orkney Islands

The analysis of 29 stomach contents collected from a colony close to Pirie Peninsula, South Orkney Islands, from 2 January to 18 February 1995, showed that fish were by far the most important prey of the Antarctic shag Phalacrocorax bransfieldensis, followed by octopods, decapods and gammarids. The fish Notothenia coriiceps constituted the bulk of the diet; however, its importance decreased by the end of the study when Lepidonotothen nudifrons was the most important prey. The composition of the stomach contents varied throughout the breeding season according to changes in the chicks' energetic demands; as chicks grew older the adults increased the mass of the loads carried to the nests, preying on larger fish, a phenomenon also observed at the South Shetland Islands. Received: 3 July 1996 / Accepted: 9 March 1997     

Lanternfish (Myctophidae) in the diet of the Cape petrel Daption capense at the South Shetland and South Orkney Islands, Antarctica

All of the fish identified in stomach contents and regurgitations of breeding and chick Cape petrels collected during January and February 1996 at Fildes Peninsula and Harmony Point, both in the South Shetland Islands and at Laurie Island, South Orkney Islands, were myctophids, a family never previously reported in the diet of breeding Cape petrels. Electrona antarctica was the most important fish prey, followed by Electrona carlsbergi at Fildes Peninsula, Krefftichthys anderssoni at Harmony Point and Gymnoscopelus braueri at Laurie Island. The absence of Pleuragramma antarcticum in the diet of this petrel, which is considered a P. antarcticum-feeder, is discussed. Received: 22 December 1997 / Accepted: 6 June 1998     

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 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     

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     

Metal (Fe, Zn, Mn and Cu) levels in the Antarctic fish Notothenia coriiceps

During the 1994/1995 Antarctic summer 20 Antarctic cod (Notothenia coriiceps) of both sexes were collected at King George Island, South Shetland Islands, Antarctica, to determine the levels of Fe, Zn, Mn and Cu in muscle, liver, gonad and kidney. Metal levels were assessed using the inductively coupled plasma-atomic emission spectrometry (ICP-AES) technique. The levels of Fe, Zn, Mn and Cu observed in both sexes of N. coriiceps were significantly lower in muscle tissue than in liver, kidney and gonad; the livers of males and gonads of females had the highest levels. The differences between the sexes were significant for Zn and Mn in gonads and for Cu in liver. Despite the modest size-range of the specimens, the Cu levels in liver, muscle and kidney were significantly inversely correlated with female mass (P < 0.05) as was gonad Cu level and male body length. Fe mainly presented the highest concentrations and Cu and Mn the lowest ones. Mean muscle metal levels are similar to those of hake, cod, herring and mackerel; however, the level of Fe was slightly higher. Accumulation may occur for Fe, Zn and Mn in liver, kidney and gonad, which have higher levels than those of most prey. Received: 21 October 1997 / Accepted: 1 February 1998     

The role of the rock cod Notothenia coriiceps Richardson, 1844 in the life-cycle of Antarctic parasites

Fifty specimens of Notothenia coriiceps caught in Potter Cove, King George Island, were examined for ecto- and endoparasites. Of the 22 parasite species found, 18 were helminths, 2 were hirudineans and 2 were crustaceans. The isopod Aega antarctica and an unidentified hirudinean are reported for the first time from this fish host. Dominant parasites were the adults of Aspersentis megarhynchus, the invasive stage of Corynosoma spp. (cystacanth) and the adults of Macvicaria pennelli, with respective prevalences of infestation of 94, 76 and 74%. The preferred sites of infestation were the pylorus and intestine, where five different larval (nematodes and cestodes) and eight adult (digeneans and acanthocephalans) parasite species were found. No adult nematodes and cestodes were found and no parasites could be isolated from the musculature. The results of the present study are related to previous findings on the parasite fauna of N. coriiceps. The comparison implies a high parasite diversity in this benthic Antarctic fish species. Most parasites found appear to have a wide range of distribution within Antarctic waters together with a low host specificity. Besides its role as final host for several species of trematodes and acanthocephalans, N. coriiceps serves as transmitter of parasite larvae to piscivorous birds and seals. It is concluded that the parasite fauna in Antarctic fish species provides important insights into the different habitat use and trophic relationship of their fish hosts. Received: 11 September 1997 / Accepted: 12 January 1998     

Body size, sex ratio and diet composition of Arctogadus glacialis (Peters, 1874) (Pisces: Gadidae) in the Northeast Water Polynya (Greenland)

Little is known about the biology and feeding ecology of Arctogadus glacialis (Peters, 1874), an endemic gadid fish species occurring circumpolarly in both ice-free and ice-covered Arctic seas. In this study we analysed specimens sampled from bottom trawl and Agassiz trawl catches conducted at eight stations in water depths from 115 to 490 m in the Northeast Water Polynya off Greenland in August 1990. Size composition and sex ratios were assessed for 585 fish with standard lengths ranging from 7.8 to 34.5 cm. Median fish sizes at the stations ranged between 8.6 and 18.8 cm. Quantitative stomach content analyses of a subsample of 175 specimens revealed that in the Northeast Water A. glacialis fed almost exclusively on pelagic prey. Truly benthic organisms were not found in the stomachs, and sympagic species were rarely recorded. Overall, calanoid copepods were the major prey in terms of numbers. However, stomach contents varied considerably between fish size groups. In terms of prey biomass, copepods dominated the diet of small fish (<12 cm), primarily occurring at shallow stations (115–250 m), whereas amphipods and mysids were relatively more important for larger fish (>16 cm), which dominated the catches at deep stations (360–480 m). The broad variety of diet composition indicated an opportunistic pelagic feeding pattern. Received: 6 November 1997 / Accepted: 11 May 1998     

Chaetoceros resting spores in the Gerlache Strait, Antarctic Peninsula

The formation of resting spores in diatoms is a common phenomenon in neritic environments. Here we report on resting spores of the genus Chaetoceros associated with a layer of increased chlorophyll fluorescence, at a depth of more than 200 m, north of Brabant Island and in Wilhelmina Bay, southeast coast of the Gerlache Strait (64°41.0′S, 62°0.5′W). Six species of Chaetoceros were identified by the morphology and size of the resting spores. Given that Chaetoceros spp., both in vegetative cells and as resting spores, are commonly found in Antarctic coastal surface waters, their location at depth could represent the pelagic “waiting” or “seeding” populations mentioned for other environments. Received: 25 November 1996 / Accepted: 16 November 1997     

Interannual study of Chinstrap penguin’s diet and reproductive success at Laurie Island, South Orkney Islands, Antarctica

Inter-annual variability in the diet of Chinstrap penguins (Pygoscelis antarctica) at Laurie Island, South Orkney Islands was examined based on stomach contents of adults coming ashore during the 1997/1998–2001/2002 breeding seasons. Krill (Euphausia superba) dominated the diet either as frequency of occurrence (in 100% of samples), number (>99%), and percentage contribution in weight (>99.5%). Other prey items were minor but did vary between years. The contribution in weight of fish, amphipods and cephalopods ranged between 0.01–0.5, <0.01–0.14 and 0–0.03, respectively. Although minor components varied slightly along the years, the weight of stomach contents was significantly different. It was found that for a given weight the maximum observed percentage of undigested krill resulted negatively correlated with the stomach contents total weight. The proportion of whole krill observed in individual penguins, expressed as a fraction of the maximum corresponding to its weight was used to characterize the prevailing conditions in each season.     

A new species of Myriochele (Polychaeta, Oweniidae) from Antarctica, with considerations on the Antarctic oweniids

A new species of Oweniidae from the Ross Sea (Antarctica) is described and compared with the remaining species of the genus Myriochele from the Antarctic seas. The authors also discuss the difficulty of detecting the shape of uncini (considered as an important diagnostic character) by optical microscopy; they propose a key to Antarctic Oweniidae based on characters easier to observe than uncini. Received: 14 October 1997 / Accepted: 16 December 1997     

Semi-quantitative study of macrobenthic fauna in the region of the South Shetland Islands and the Antarctic Peninsula

During the BENTART 95 Expedition, 24 Agassiz trawls for macrozoobenthos sampling were carried out at depths of 40–850 m, from north of Livingston Island to the Antarctic Peninsula. The samples were analysed using a semi-quantitative method, and with the resulting numerical data, transformed into a six-point scale, we constructed a Bray-Curtis similarity matrix. A total of 74,624 specimens, belonging to 38 taxonomic groups, were collected. The most abundant group was Polychaeta Sedentaria, with 36% of the total, whereas the highest relative masses were from Ascidiacea (23%), Echinoidea Regularia (18%) and Ophiuroidea (16%). The maximum number of specimens recorded was 15,600 ind./50 l. Cluster analysis separated stations located in Foster Bay (Deception Island), characterised by low taxonomic richness and high relative mass (average: 26.7 kg). A zonation of ascidians, regular sea urchins and ophiuroids was observed at Deception Island, clearly related to depth and substratum type. The remaining stations were separated into two groups. The first one comprised the shallowest stations (40–130 m), dominated by sessile active filter-feeders, belonging to Ascidiacea, Demospongia and Bryozoa, and probably related to high primary production zones. The second group comprised deeper stations and was dominated by classes exhibiting a diversity of trophic strategies: Ophiuroidea and Asteroidea, to 400 m, and Polychaeta Sedentaria at greater depths. Received: 20 February 1997 / Accepted: 8 September 1997     

How important are pelagic preys for the kelp gull during chick-rearing at the South Shetland Islands?

An analysis of pellets regurgitated indicated adult kelp gulls (Larus dominicanus) on the South Shetland Islands consumed predominantly intertidal prey, whereas previous studies at Antarctic Peninsula sites have reported kelp gulls consuming predominantly pelagic species. The pellets collected at Nelson Island during the chick-rearing period indicated that the limpet Nacella concinna was their most frequent prey, followed by carrion, gammariids, snails and krill. Fish were scarcely represented. Also, regurgitated stomach contents of chicks showed that limpets and carrion were the most frequent food items, accounting for 70% of the mass. However, gammariids were particularly important by number. Significant differences were observed in the overall comparison of the diet as reflected by the two sampling methods. In general, the importance of pelagic prey was negligible when compared to intertidal or scavenged prey. Our results differ greatly from those reported for the Antarctic Peninsula, where chicks were almost exclusively fed with the pelagic fish Pleuragramma antarcticum. These differences could be related to the abundance of pelagic resources in southernmost latitudes, and/or to the presence of more extensive intertidal foraging areas at the South Shetland Islands. Received: 7 October 1996 / Accepted: 14 July 1997     

Christensenia, a new terrestrial enchytraeid genus from Antarctica

Christensenia gen. nov., C. blocki sp. nov., is described from Signy Island, South Orkney Islands, maritime Antarctic. The new species is identical with specimens that Stephenson (1932) determined as Marionina georgiana (Michaelsen, 1888), but differs from the type material of M. georgiana. The species M. georgiana (Michaelsen, 1888) is also placed in the new genus Christensenia, the main characteristics of which are: possession of sigmoid setae, and the presence of large numbers of small, hyaline, stick-like, anucleate lymphocytes. No other types of lymphocyte are observed. Oesophageal appendages and intestinal diverticulae are absent. Dorsal vessel originates in the clitellar region; blood is colourless. The anteseptal part of the nephridium consists of the funnel and a few canals, with the efferent duct arising postero-ventrally. Spermathecae are without diverticulae, entally connecting with the oesophagus. The known distribution of the genus is currently limited to terrestrial habitats in the sub- and maritime Antarctic. Received: 24 June 1996 / Accepted: 20 October 1996     

Feeding plasticity of the Antarctic fish Trematomus hansoni Boulenger, 1902 (Pisces: Nototheniidae): the influence of fishery waste on the diet

The consumption of fishery waste by the Antarctic bottom-dwelling fish, Trematomus hansoni, is described in the Cosmonaut Sea. The study indicates that T. hansoni is able to switch its feeding habits at the time of fishery operations by incorporating fishery waste into the diet. Received: 22 September 1997 / Accepted: 21 November 1997     

Feeding biology of the Antarctic brittle star Ophionotus victoriae (Echinodermata: Ophiuroidea)

Summary The diet and feeding behavior of the brittle star Ophionotus victoriae were studied in 1981–1983. Frequency-of-occurrence and points methods were used to examine stomach contents of 2475 specimens from 19 stations representing seven general localities along the Antarctic Peninsula and South Sandwich Islands. Results of the two methods were in agreement and indicated this species is an opportunistic generalist with high diet plasticity. The most abundant component of the stomach contents was sediment but the diet derived from at least 13 phyla. Crustaceans, notably euphausiids and amphipods, were most important at some locations. Diet composition varied significantly between locations and years, but did not differ among brittle star size groups. Stomach content data and laboratory studies indicate that O. victoriae utilizes a variety of feeding methods but not suspension feeding.     

Suprabenthic assemblages from South Shetland Islands and Bransfield Strait (Antarctica): preliminary observations on faunistical composition, bathymetric and near-bottom distribution

During austral summer 1995 suprabenthic assemblages were investigated at 24 stations located around Livingston Island, Deception Island and Bransfield Strait, at depths ranging from 45 to 650 m. Suprabenthos was collected on R/V Hesperides using a Macer-GIROQ sledge with an automatic opening and closing system. This study presents data on the occurrence and relative abundance of the main suprabenthic groups collected in the water layer immediately adjacent to the bottom (10–140 cm above bottom). Commonest groups were Amphipoda, Mysidacea, Isopoda, Cumacea and Euphausiacea. The distribution and spatial separation in the suprabenthic habitat of the main groups are discussed. Received: 20 February 1997 / Accepted: 14 July 1997     

Congruence of electrical properties in two Antarctic and two middle-latitude marine species of Euplotes (Ciliata, Hypotrichida)

Electric membrane properties and motor behaviour of two Antarctic and two middle-latitude species of Euplotes were compared. Membrane potential fluctuations and whole-cell currents were measured using the whole cell clamp. The electrical properties of both of the Antarctic species between themselves and of both of the middle-latitude species are nearly identical. Furthermore, after warming up to 22°C, the Antarctic species grown at 4°C show the same pattern of spontaneous potential fluctuations, induced potential oscillations and membrane currents as the middle-latitude species grown and measured at 22°C. After cooling down to 4°C, the middle-latitude species grown at 22°C show the same electrical properties as the Antarctic species grown and measured at 4°C. The congruence of the temperature-dependent electrical properties in Euplotes species from completely different habitats is presumably based on a universal mechanism of temperature dependence of ionic conductances, indicating the close physiological relationship among the species. Received: 29 October 1997 / Accepted: 20 April 1998     

Dorymenia troncosoi sp. nov. (Mollusca Solenogastres: Proneomeniidae), a new species from the South Shetland Islands (Antarctica)

During the Spanish oceanographic expedition BENTART '95, carried out in Antarctic waters off Livingston Island (South Shetland Islands), five small specimens of a new species of Solenogastres-Cavibelonia, Dorymenia troncosoi sp. nov., were collected at a depth of 65–240 m on a silt bottom. The species is characterized by the presence of a pallial cavity with four pouches (a dorsal, two lateral and a ventral pouch), seminal receptacles that open into the spawning ducts through a short duct, radula having 9–11 teeth per row (1 central and 4–5 lateral, all the same size), the end of the copulatory spicules having a cross-section in the shape of a four-pointed star, and abdominal spicules present. These characteristics separate this species from other species of the genus, particularly from Dorymenia profunda, which is the most similar. Received: 9 April 1998 / Accepted: 12 June 1998