ALBERT

Description: Levels of genetic diversity and population differentiation were examined in temporally (1990 to 1997) and geographically separated samples of the argentine short-finned squid Illex argentinus using 7 microsatellite loci. Number of alleles (mean number of alleles per locus over all samples = 24.1) and heterozygosity (mean observed heterozygosity per sample = 0.84) were high for all samples, indicating that these loci have a greater potential utility for investigating population genetic structure than allozyme markers used in previous studies. Genetic diversity did not differ significantly between samples taken 5 yr after commencement of the fishery (1990) and those collected during a period of progressively intense fishing pressure (1994 and 1997). Several small but significant differences in between-sample genetic variation (FST) were observed, but these could not confirm the previous suggestion of cryptic species or several well-defined stocks within the fished population.

Description: The fishery for Illex argentinus in the Southwest Atlantic is subject to large inter-annual variability in recruitment strength. In this paper we attempt to build a predictive model using sea surface temperature (SST) to examine links between recruitment to the Falkland Islands fishery and environmental variability during the juvenile and adult life history stages. SST data from the National Center for Atmospheric Research (NCAR) were found to be comparable with near-surface data derived from in situ expendable bathy-thermograph (XBT) profiles in the southern Patagonian shelf. Variation in SST during the early life stages appears to be important in determining recruitment of I. argentinus. SST in the hatching grounds of the northern Patagonian shelf during the period of hatching (particularly June and July) was negatively correlated with catches in the fishery in the following season. SST anomaly data from positions in the Pacific and Southwest Atlantic were used to examine teleconnections between these areas. Links were seen at a lag of 2 yr between the Pacific and southern Patagonian shelf, and at about 5 yr between the Pacific and northern Patagonian shelf. This is consistent with SST anomalies associated with El Niño in the Pacific propagating around the globe via the Antarctic Circumpolar Wave (ACW). Predicting cold events via teleconnections between SST anomalies in the Pacific and Atlantic would appear to have the potential to predict the recruitment strength of I. argentinus in the Southwest Atlantic.

Description: Cephalopods play an important role in the trophic web of the Southern Ocean, but little information is available on their biology. The 2 largest sub-Antarctic seabirds, the king penguin Aptenodytes patagonicus and the wandering albatross Diomedea exulans, feed primarily on squids during the austral winter at the Crozet Islands. We examined a large number of accumulated cephalopod beaks in the stomach of these birds together with some undigested items; first, to understand how these 2 predators share the squid resource during winter, a period of supposed low food availability, and, second, to use a diving and a flying seabird as biological samplers of Southern Ocean cephalopods. Individuals of the family Onychoteuthidae formed the bulk of the squid diet, accounting for 72.6 and 57.0% of the number of lower beaks in samples from king penguins and wandering albatrosses, respectively. Seven different species were identified, the 3 main squids being Kondakovia longimana (38.8 and 28.0% by number for penguins and albatrosses, respectively), Moroteuthis ingens (13.5 and 26.2%) and M. knipovitchi (20.1 and 2.3%). Both seabirds preyed upon the same cephalopod species, but penguins primarily took small- to medium-sized juveniles (99.0% of the onychoteuthids) and albatrosses preyed on larger adult specimens (96.0%). Fresh remains indicated that adult K. longimana and M. ingens were mature individuals which, as shown by satellite tracking of albatrosses, were taken over the slope and nearby oceanic waters surrounding the archipelago. The present study indicates that mating/spawning of K. longimana and M. ingens occurs in Crozet waters during the winter months. It also extends the biogeography of K. longimana to north of the Antarctic Polar Front, in the Polar Frontal Zone, where it has not previously been recorded.

Description: The marine habitat exploited by black-browed Diomedea melanophrys and grey-headed albatrosses D. chrysostoma breeding at Campbell Island, New Zealand, was studied using satellite telemetry. Data were analysed in relation to the bathymetry and sea-surface temperature of the foraging zones. Black-browed albatrosses spent 55% of their time on the Campbell Plateau but also carried out long foraging trips to the Polar Front and Antarctic Zone at a distance of over 2000 km. They relied heavily on juvenile Micromesistius australis, a schooling fish, during foraging trips to the shelf but over oceanic waters the squid Martialia hyadesi was the main prey taken. Grey-headed albatrosses spent 71% of their time foraging over the deep waters of the Polar Frontal Zone where M. hyadesi comprised over 90% of the mass of prey taken. No satellite-tracked birds fed over the shelf, but data from the duration of foraging trips and dietary analysis suggests that shelf-feeding is important for this species. Significant inter-species differences in the time spent in neritic and oceanic zones show that black-browed albatrosses are reliant primarily on shelf resources while grey-headed albatrosses are primarily oceanic feeders. In addition, the 2 species overlapped little in the zones used over oceanic waters, with black-browed albatrosses feeding in more southerly waters than grey-headed albatrosses. However, both species feed on M. hyadesi when foraging in association with the Polar Front.

Description: It has often been suggested that, given their large food requirements, sperm whale Physeter macrocephalus distributions should reflect the distribution of productive ocean environments, and it seems therefore that chlorophyll concentration might be a good indicator of sperm whale distribution. To examine the existence of such a relationship, and to determine over which sclaes it occurs, sperm whale density was correlated with phytoplankton pigment concentration over a range of spatial and temporal scales. Sperm whale distribution was detrmined using records of kills from 19th century Yankee whaling, and the distribution of pigment concentration from satellite colour observations averaged over 8yr interval. These measures were compared over scales of 220km square to 1780km square. The distribution of sperm whales in the temperature and tropical Pacific Ocean was associated with distributions of phytoplankton pigment over every spatial scale considered, and the coefficient of correlation increased with increasing spatial scale. However, a few exceptions to this scheme were found, implying that other factors would be of importance in some regions. This study confirmed the existence of space lag and a time lag between a peak in chlorophyll concentration and a peak in sperm whale density. It also demonstrated that over large spatial scales, and when the data are averaged over large temporal scales, chlorophyll concentration is a good indicator of sperm whale distribution and that over these scales ocean colour recorded from space could help predict areas of high or low sperm whale density.

Description: Stomach contents from 30 long-finned pilot whales Globicephala melas captured incidentally in the Distant Water Fleet (DWF) mackerel fishery off the northeastern United States were examined. Several methods of assessing prey importance were used in order to construct a true representation of the pilot whale diet. Separate analyses of trace (free, durable body parts from well-digested prey) and non-trace (relatively intact prey) food materials were conducted to address biases caused by differential rates of digestion and passage. Squids dominated the diet and long-finned squid Loligo pealei was the most important prey, but we noted large yearly fluctuations in prey importance. Metric multidimensional scaling analyses of trace and non-trace stomach contents of individual whales suggest that many animals were cuaght while feeding opportunistically near fishing operations, resulting in a bias of non-trace (intact) stomach contents. The diversity of prey in this study was greater than previous reports of the food habits of western North Atlantic non-finned pilot whales.

Description: We investigated the foraging location, diving behaviour, dietary composition, feeding rates and foraging trip durations of emperor penguins Aptenodytes forsteri raising chicks at the Auster and Taylor Glacier colonies on the Mawson Coast of Antarctica in the winter, spring and early summer of 1993, to examine seasonal changes in the penguins' foraging ecology. As day-length increased after winter, the penguins' daily swimming time increased from 7.83 ± 1.50 h in August to 12.23 ± 1.25 h in September and 12.95 ± 1.24 h in October. Accordingly, the penguins' dive rate increased from 92.7 ± 28.5 to 149.4 ± 23.4 and 161.6 ± 19.3 dives d-1 in the respective months. The birds targeted prey in the vicinity of the continental slope mainly at depths 〈100 m, although some individuals frequently hunted at depths 〉200 m, and the maximum depth achieved was 438 m. Antarctic krill Euphausia superba were the most common prey taken overall, 41% of the diet by mass, and dominated the diets between August and October. The contribution of Antarctic krill to the diet reduced over time from 68% in August to 1% in early December. In November, the glacier squid Psychroteuthis glacialis dominated the diet (47 to 63%), and in early December the diet comprised various species of fish, Trematomus species (27%), Pagothenia borchgrevinki (24%), and Pleuragramma antarcticum (8%), and squid, P. glacialis (13%) and Alluroteuthis antarcticus (9%). The birds' prey consumption rates more than doubled between late winter and early summer, from 4.0 ± 1.0 to 8.7 ± 1.7 kg d-1 spent foraging; these values are equivalent to metabolisable energy intakes of 628 ± 134 and 1422 ± 308 kJ kg-1 d-1, respectively. During brooding (late winter to early spring), females spent less time at sea than males (8.7 ± 2.7 vs 17.7 ± 3.8 d); thereafter trip durations of both sexes were similar and declined from 15-19 d in spring to 〈10 d in early summer. Between hatching and about 1 wk prior to fledging each parent fed its chick 7 or 8 times. To raise a chick, females and males consumed approximately 410 and 470 kg of prey respectively, or 880 kg for each breeding pair. Seasonal variations in the penguins' foraging were probably influenced by fluctuating sea-ice conditions, differences in the prey types available, changes in day-length toward summer, and increasing demands of the growing chicks.

Description: A survey of parasites in 600 short-finned squid Illex coindetii (Vérany, 1839) taken from 2 locations (north and south Galicia) off the northwesterb Iberian Peninsula revealed the presence of numerous somatoxenous helminths. Three genera of Tetraphyllidean plerocercoids were represented (prevalences: Phyllobothrium sp., 45,7%; Dinobothrium sp., 0.8%; and Pelichnibothrium speciosum, 0.001%); 1 Trypanorhynchidean metacestode was also present (Nybelinia yamagutii, 0.4%). In addition, larval nematodes of Anisakis simplex (L3) were recorded (10.6%). Abundance of infection was examined in relation to squid sex, standard length, maturity and locality. This analysis indicated that parasite infection was lower in the southern squids than in the northern squid group. Over the entire survey area, parasite infection showed a positive correlation with host life.cycle, often with the greatest number of parasites among the largest and highest maturity individuals (〉18 to 20cm; maturity stage V).

Description: Predator data and exploratory fishing in the Scotia Sea have revealed the presence of cephalopod stocks in the Antarctic Polar Frontal Zone (PFZ). This is a vast, remote region where large epipelagic cephalopods aggregate into highly mobile schools making them difficult to locate and sample. We used satellite tagged predators and shipboard acoustics for coarse and fine scale location of cephalopods concentrations, and sampled them with commercial and scientific nets to determine the relationship between cephalopod distribution and mesoscale oceanographic features at the PFZ. Saltellite tags were attached to 9 grey-headed albatrosses Diomedea chrysostoma, breeding at Bird Island, South Georgia, to monitor foraging at sea in January-March 1994. A foraging area at the PFZ, north of South Georgia, was located, an acoustic survey undertaken and a fixed situation established where gular midwater trawl 25m² (RTM25), a horizontal multiple plankton sampler and a neuston net. Acoustic layers were targeted and the RMT25 sampled 200m layers to 1000m in daylight and darkness. Cephalopods were simultaneously recovered from food samples fed to D. chrysostoma chicks at Bird Island. Two CTD transects, approximately normal to the major current flow, were undertaken across the PFZ and remote-sensed-sea-surface temperature images from NOAA polar orbiting satellites that exploited by D. chrysostoma. The largest and most conspicious species was the ommastrphid squid Martialia hyadesi which is the most important cephalopod prey species. Net-sampled M. hyadesi had been feeding on crustaceans and mesopelagic fish. The cephalopod community was sampled in a feature, interpreted as a warm core ring, in an area characterised by mesoscale features associated with the bathymetry of the northern end of the Northeast Georgia Rise and near a gap in the Falkland Ridge. The association of these mesoscale features with the bathymetry suggests that they may be predictable foraging locations for the cephalopods and their predators.

Description: An experimental laboratory set-up was used to study the influence of different grain size compositions and temperatures on the growth of benthic cyanobacteria and diatoms, and on the competition between these 2 groups. Monospecific cultures of 3 species of cyanobacteria (Merismopedia punctata, Microcoleus chthonoplastes, Oscillatoria limosa), and of 2 species of benthic diatoms (Phaeodactylum tricornutum and Nitzschia sp.) were used. The organisms were cultured in 100 ml flasks filled with medium and 3 different kinds of sediment: (1) Sand (fine sand, 63 to 200 µm), (2) Mud-I (mixed fine sand and mud 〈63 µm in the ratio 80:20 wt %), (3) Mud-II (mixed fine sand and mud in the ratio 50:50 wt %). Experimental temperatures were 10, 15 and 25°C. At 10°C and 15°C, both diatom species achieved the highest biomass on the sediments of the finest grain size (50 wt % 〈 63 µm) while cyanobacteria achieved low biomass levels. Coarsening of sediments at the same temperature levels revealed a gradually lower biomass of the diatoms. Particularly on sand, the diatoms never reached the same concentrations of chlorophyll a as on mud. The cyanobacteria, on the other hand, had the highest biomass on sand at 15°C. In the competition experiments the benthic diatom species Nitzschia sp. dominated all types of sediments at 10°C and 15°C. The experiments at 25°C were dominated by the filamentous cyanobacterium M. chthonoplastes. This indicates the importance of abiotic conditions for the distribution and abundance of benthic phototrophic micro-organisms.