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Pinniped and seabird research was conducted by the Southwest Fisheries Science Center at Seal Island, South Shetland Islands, Antarctica, during the 1995-1996 austral summer (see Martin, Hewitt, and Holt, Antarctic Journal, in this issue). The National Oceanic and Atmospheric Administration (NOAA) maintains a field camp at this location which is occupied annually. This long-term research project focuses on the relationship of top predators (fur seals and seabirds), their prey (krill and fish), and their surrounding environment. These studies are conducted in support of the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR) Ecosystem Monitoring Program (CEMP). Due to the impending closure of the Seal Island camp site and efforts to select a new site, objectives of the 1995-1996 field season were abbreviated from previous years and were as follows:
Weights of 101 antarctic fur seal pups (51 female, 50 male) were measured on 27 January 1996. Male pups weighed on average 13.51 kilograms (standard deviation, 2.00), and female pups weighed on average 11.58 kilograms (standard deviation, 1.57). These average weights for this period in the season were the heaviest recorded since 1991-1992 for both male and female pups. Because of the abbreviated field season, the exact pupping chronology is not known. The heavier than normal weights could be attributed to a shift in breeding chronology, or increased availability of prey. The 1995-1996 Antarctic Marine Living Resources (AMLR) Field Season Report notes higher than normal krill abundance estimates (Martin 1996).
At least 281 pups were born on Seal Island during the 1995-1996 austral summer. Pup counts commenced approximately one month after the typical peak in seal pupping occurs, so it is reasonable to assume this number was larger earlier in the season. It is very close, however, to the previous two seasons' birth totals of 286 (1994-1995) and 299 (1993-1994). A census of nearby rookeries (Large Leap and Cave Colony) on 5 February 1996 yielded 288 and 101 pups, respectively. Total births for the Seal Island archipelago were at least 670 for the 1995-1996 season, compared to 699 for the 1994-1995 season, and 666 for the 1993-1994 season.
Seventy-four known-aged fur seals (34 males, 40 females) tagged as pups from the 1986-1987 to 1993-1994 austral summers were sighted in 1995-1996. Of the 40 females, 16 were sighted with a pup. Long-term resight data should provide estimates of age at first reproduction, and cohort and age specific mortality.
Ten chinstrap penguin colonies were censused on 28 January 1996 at approximately 2/3 creche. In total, 1,097 chicks were counted, the lowest count for these colonies in the 7 years of the census, which averaged 1,511 chicks. One of the 10 colonies did not exist for the first time since the census began. Timing of the start of chinstrap chick fledging, 16 February 1996, and mean fledgling weight, 3.12 kilograms (standard deviation, 0.32), were consistent with previous seasons. This agreement would suggest the decline in the breeding population was not due to a decrease in prey available during the breeding season.
Census of all macaroni penguin colonies on 26 January 1996 at approximate completion of creche yielded 194 chicks. This number is slightly lower than average (203) for the last 7 years of census.
From the 1987-1988 austral summer to the 1993-1994 austral summer, approximately 2,000 chinstrap chicks and 70 macaroni chicks were banded each year. In 1995-1996, 444 known-aged chinstrap penguins and 34 known-aged macaroni penguins were sighted. Chinstrap penguins 2-4 years old constituted 86 percent of the resights, whereas 5-8 year olds made up only 14 percent. These resights can provide data on age and cohort specific mortality, age at first reproduction, and breeding success of age classes.
The authors would like to thank the officers and crew of the R/V Yuzhmorgeologiya for their significant logistical support. This research was supported by NOAA's National Marine Fisheries Service as part of the AMLR program.
References
Martin, J.E. (Ed.) 1996. AMLR 1995/96 Field Season Report (Southwest Fisheries Science Center Administrative Report LJ-96-15.) La Jolla: Southwest Fisheries Science Center.
Martin, J.E., R.P. Hewitt, and R.S. Holt. 1996. The U.S. Antarctic Marine Living Resources (AMLR) program: 1995-1996 field season activities. Antarctic Journal of the U.S., 31(2).