CCAMLR

Hatching season and larval growth of Pleuragramma antacticum in the water off Antarctic Peninsula were determined by the examination of growth increments in otoliths. The samples were collected by Bongo plankton net or MOCNESS from December 1993 through January 1994. P. antacticum was predominated (54 inds. out of 77 fish larvae) in ichthyoplankton samples, and occurred mainly in cold water of the Weddell Sea. Body length of P. antacticum ranged from 12.0 to 67.3 mm. Otolith radii (R) ranged from 150 to 260 μm, and linearly related to body size (L); R = - 43.6 + 5.99 L (r2=0.79). The mean size of otolith cores was about 50 μm in diameter. The width of the growth increments was narrow near the core, but it became broader at around 50 - 100th increments (ca. 1.3 μm). However, it decreased thereafter toward the edge maintaining the size of ca. 0.5 μm. Assuming that a growth increment was deposited daily after hatching, P. antacticum seems to be hatched during June - July, because the mean number of increments was 178.3 (standard deviation = 12.8). With the samples we examined, we speculate that there exist two hatching periods for P. antacticum: The large larvae (40-50 mm) hatched in winter (June - July), while the small ones in early summer (December) .

The distribution of kri!! harvesting effort and associated catch rates has previously only been available to the scientific community in the form of sub-area or fine-scale(0.5 ° latitude by 1 ° longitude) recorded statistics. Earlier analyses of these data have shown this was a shelf-break fishery over much of the Scotia Sea. Although these statistics give a general idea of where the fishery has operated they do not reveal the localised nature of the fishing operation. In particular they give little ecological insight into how the fishable aggregations relate to the local environmental conditions. Over the last three winter fishing seasons (1993-1995) haul by haul statistics have been recorded in the South Georgia area. Analyses of these data show marked interannual variability and indications of a seasonal pattern. In 1994 the fishery was almost totally based over a large shallow bank area on the north-east shelf edge. During 1995 the fishery was still predominantly in this area but also operated further west on a range of banks associated with submarine canyons. The data for 1993 were only available from August but the fishery was restricted in that period to an area on the western edge of the shelf break where negligible fishing occurred in the following two seasons. The results are discussed in relation to the ecology of krill and the fishery interaction with the local predator colonies.

Adelie penguins are long-lived, highly philopatric seabirds that dominate the bird biomass of the Western Antarctic Peninsula region, and serve as focal animals for our Long Term Ecological Research (LTER) study of the effects of environmental variability on animal populations in the Antarctic marine ecosystem. The major physical factors affecting the breeding success, distribution and demography of Adelie penguins in the Southern Ocean are variability in sea ice cover, ocean circulation patterns and terrestrial topography. We analyzed Adelie distributions in the Antarctic Peninsula region and concluded that Adelie penguins have discrete subpopulations in the northeastern and southwestern regions of the area. These subpopulations are separated by a 400 km gap in their respective distributions, but each is within several hundred kilometers of predictable pack ice areas in the Weddell and Bellingshausen Seas, respectively. We propose that these pack ice areas are the wintering grounds for each subpopulation, and that access to these pack ice areas, early in the season following courtship fasting, is the key to successful breeding in Adelies. We further analyzed the colony distributions within each subpopulation and found highly clumped distributions of Adelie penguins that were strongly correlated to physical factors such as bathymetry, currents and wind direction. We propose that these variables reduce the occurance of pack ice in the vicinity of breeding colonies of Adelie penguin populations, thereby assuring access to open water in the early season. Finally, we examined the influence of the interaction of local topography and weather on the size, location and persistence of breeding groups within Adelie penguin colonies. Snow accumulation, melt water runoff and solar radiation all impact the microclimate of breeding colonies and influence the selection of nesting sites among Adelie penguins. The abandonment of breeding areas by Adelie penguins, following two to three years of failure at "poor" sites, suggests that changes in the population distribution of Adelie penguins may be very rapid in response to changing environmental conditions, such as increased snow deposition. Adaptations to environmental variability are seen in every aspect of the natural history of the Adelie penguin, from the distribution of subpopulations around Antarctica, to the sizes and distributions of colonies within regions, to the choice of breeding sites within colonies.