CCAMLR

Microscale data, described the Soviet krill fishery off the Elephant Island (Subarea 48.1) between 59°-62°S and 53°-57°W during the period from 21.11.1988 to 25.03.1989, are analysed. Though the catch of the USSR in the above-mentioned season reached maximum, the total fishery intensity for the last 9 seasons was low and only 1 standard vessel operated in the area during 40% of the period. The highest catch per-unit-of-effort was observed in January (7.7 t per hour of trawling in average), and the lowest in November (3.5 t per hour of trawling in average). Fisheries tacktics follows the scheme: 1) vessels enter the Elephant Island area and search for krill concentrations; 2) fishing of concentrations, drifted from the Island, and return into the initial area when the concentration has been lost. The velocity of krill concentration northeastward drift, calculated by the fleet displacement amounted to 9.7-11.1 km/day (11-13 cm/sec). The analysis of fishing ground allocation by five-day periods showed that fleet operation areas in general overlap the minor part of foraging zones for animals, preyed on krill. Based on this and taking in account low fishery intensity the conclusion was made that current krill fishery insignificantly affect the seals and birds, preyed on krill.

A nest ANOVA design was used to measure the variance component due to differences between individual penguins in the length of krill eaten by Adélie penguins at Esperanza Bay. The value found was not different from zero: variance component = -0.16; F = 0.93; P = 0.54. This finding supports the use of individual penguins to estimate parameters of the prey population without discriminating by sex, weight or other factors pertaining to the predator.

Since parameters of penguin populations may provide good indices of the abundance of the key prey species (krill) and thus the state of the Antarctic marine ecosystem, aerial reconnaissance and photography are used in the Ross Sea sector of Antarctica to determine where Adelie penguins (Pygoscelis adeliae) breed, and to count the numbers of nests occupied during the early incubation period and surviving chicks in mid-January (when weight and measurements of samples of chicks at Capes Royds and Crozier give a condition index). From 1981 to present, all islands and sea coasts between 158°E and 175°E were searched, and 12 previously unreported breeding rookeries were discovered. Thirty-nine Adelie rookeries are now known from the region, with a total of about 1,082,000 breeding pairs - almost half the world population. Some rookeries are photographed in all, or most, of the seasons to study the pattern of natural population fluctuations. Populations at nearly all rookeries have increased markedly in size over the last 10 years. Possible reasons for this, and for annual fluctuations in numbers breeding, include seasonal variations in sea ice and weather conditions, and longer-term climatic change. This study identifies the need for complementary Ross Sea baseline studies including: studies of primary productivity and effects of ice thickness and UV radiation, climate change, krill distribution and abundance, seasonal distribution of sea ice, air temperature at sites remote from continental influence, and satellite tracking of radio-tagged penguins to study foraging range and winter dispersion.
In 1992/93 we propose repeating the photographic surveys of rookeries on Ross Island using helicopters in December and January to count incubating adults and surviving chicks, respectively. Rookeries north of Ross Island will be photographed from an RNZAF C-130 in December. Details of methods and logistics are discussed.
In New Zealand, developing, printing, collating, filing and counting all photographs of study rookeries is completed each season.

Aerial reconnaissance and photography were used in the Ross Sea sector of Antarctica to determine the breeding locations of Adé1ie penguins Pygoscelis adeliae, and to count the numbers of nests occupied during the early incubation period. From 1981 to 1987, all islands and sea coasts between 158°E and 175°E were searched, and 11 previously unreported breeding rookeries were discovered. Thirty-eight Adé1ie rookeries are now known from the region, with a total of about 1,082,1300 breeding pairs – almost half the world population. Some rookeries were photographed in all, or most, of the seven seasons to study the pattern of natural fluctuations in Adé1ie populations, and comparisons have been made with earlier counts. Populations at nearly all rookeries have increased in size over the last 10–20 years. Possible reasons for this, and for annual fluctuations in numbers breeding, include seasonal variations in sea ice and weather conditions, and longer-term climatic change.

The numbers of Adelie penguins Pygoscelis adeliae (Hombron and Jacquinot) in the Ross Sea, Antarctica, have increased markedly over the past 10 years. Proportionally, this increase is most pronounced in McMurdo Sound, where the species’ breeding range has recently been extended 3 km south to Cape Barne (77°35’S) with the re-occupation of a former rookery that was abandoned sometime before the present century. These biological trends show remarkable synchronisation with physical evidence of climatic variation in the McMurdo Sound region. We suggest that the dynamics of Adelie penguin populations may be very sensitive indicators of changes in the Antarctic climate.

Published in: New Zealand Journal of Ecology Vol. 14 (1990)

The population dynamics of the Cape Royds rookery were modelled by computer, in order to determine the probable causes of the dramatic increase since 1980 in the numbers of Adelie penguins, Pygoscelis adeliae, breeding in the Ross Sea region, Antarctica.
Variations in the extent of sea-ice around the rookery during incubation and chick rearing cannot feasibly explain the population increase and another factor or event must be introduced, which increases chick production per breeding pair and decreases adult mortality. The timing of the event is critical and rules out the cessation of human impacts or the depletion of competing baleen whales as causal factors. The event is seen as most probably the result of a recent warming of the Ross Sea climate.

Published in: New Zealand Journal of Ecology (1991) 15(2): 117-121