INVESTIGATIONS of ANTARCTIC LIVING MARINE RESOURCES by John Bengtson

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FEA TURE

INVESTIGATIONS OF ANTARCTIC LIVING MARINE RESOURCES By John Bengtson

Atlantic Ocean

Indian Ocean

Pacific Ocean 900 East 900 West

THE search Convention undertaken for the Con- falls within seIVation of two broad Antarctic Ma- categories: rine Living Re- Pacific 1) studies of sources (CCAMLR) Ocean land-breeding pin- is an international nipeds and seabirds at agreement established Seal Island, South in 1982 which has as Shetland Islands, Antarctica; its objectives the conserva- and 2) investigations of ice- tion of all living organisms in Antarc- 1800 breeding seals in the circumpolar sea- tic waters and the maintenance of their ecological ice zone. relationships. The National Marine Mammal Laboratory (NMML) Antarctic Ecosystems Program has conducted pinniped and seabird research over the past 9 years as part Seal Island Research. of the CCAMLR Ecosystem Monitoring Program (CEMP). The underlying objectives ofWvlML' s research To date, nine field seasons have been completed at the have been to deternline what factors are primarily respon- National Oceanic and Atmospheric Administration sible for influencing the population dynamics of Antarctic (NOAA) research site at Seal Island (tat. 60o59' 14" pinnipeds and seabirds, to detect significant changes in long. 55O23' O4"W) since the 1986-87 austral summer. key components of the Southern Ocean ecosystem, and to Major objectives of Seal Island research activities, con- distinguish between changes due to commercial fISheries ducted annually from early December to mid-March, and those due to natural causes. An important asPect of have been this work has focused on understanding the relationships among upper trophic level predators such as pinnipeds and 1. To assess long-teon trends in pup growth rates seabirds, their prey, and environmental conditions. Re- and attendance patterns ashore of adult female Antarctic

AFSC Quarterly Report fur seals (Arctocephalus gaze/la) according to CEMP transnlitters also enable detennining the locations of fur protocols; seals ' offshore foraging areas. Research vessels equipped with directional radio antennae are used to fol- 2. To conduct directed research on fur seal pup pro- low the seals when they go to sea to forage. Satellite- duction, foraging behavior, diet, abundance, sUIVival linked transmitters were deployed in the 1994-95 season and recruitment; in cooperation with Japanese scientists. Such studies have been successful in evaluating the interannual vari- 3. To evaluate long-teon patterns in the breeding ability of fur seal foraging areas in relation to changing success, reproductive chronology, foraging behavior prey distribution and environmental features. chick diet, abundance, sUlVival, recruitment, and fledging size of chinstrap penguins (pygoscelis antarctica) About 15 female fur seals in the foraging trip/atten- and macaroni penguins (Eudyptes chrysolophus) accord- dance studies are also instrumented annually with time- ing to CEMP protocols; depth recorders (TDRs) to docwnent diving behavior as a measure of foraging effort expended at sea. Details of 4. To conduct directed research on penguin chick seals ' diving behavior (e. , dive depth and diel forag- growth and condition, seasonal patterns in diving behav- ing pattern) are collected in conjunction with fine-scale ior, and changes in foraging patterns throughout the hydro-acoustic sUlVeys that are conducted offshore Seal breeding season; and Island by the NOAA research ship Surveyor which al- lows subsequent comparisons of fur seal dive profiles 5. To investigate the relationships among seabirds' and the horizontal and vertical distribution of Antarctic and pinnipeds' perfoonance (behavior and vital rates), krill (Euphausia superba). prey availability, and environmental features. Seabirds Antarctic Fur Seals Several census protocols have been established at Seal Daily censuses are made of tagged juvenile and adult Island to monitor the intra- and interannual trends in the seals and of pups of the year. These counts provide a re- penguin nesting population, egg and chick production, cord of the reproductive history of adult females, pup and suIVival of offspring. More than 20 000 chinstrap production, and age-specific survival rates in each field penguins nest at Seal Island in most years. The island' season. Approximately 299 Antarctic fur seal pups were breeding colonies of macaroni penguins (299 nests in born on Seal Island during the 1993-94 season, an in- 1993-94) reflect a small population near the southern ex- crease of 20% since obseIVations began in 1986-87. The tent of the species range. Following the Standard Meth- pup counts also provide insight into preweaning mortal- ods established by CEMP, selected study colonies of ity rates. Predation of fur seal pups by leopard seals both species are routinely obseIVed to provide various (Hydrurga /eptonyx) is a major source of pup mortality measures of reproductive effort and success (e. , daily at Seal Island, with as many as 50% of pups killed prior checks of marked nests to assess the sUIVival of eggs to weaning. During each sampling period, an attempt is and chicks throughout the nesting season). The chronol- made to weigh at least 100 fur seal pups. Pups are ogy of reproductive events is also monitored so that an- weighed at approximately 14-day inteIVals from late De- nual indices of reproduction and foraging can be cember to late February. The sex of weighed pups is re- standardized by time in the breeding season. corded as part of a study evaluating the differential growth rates of male and female pups, which vary from Samples of chinstrap chicks are weighed weekly to year to year. provide an index of growth rates from hatching through fledging, at which time daily samples of fledged chicks During their 4-month lactation period, female Ant- are weighed as they loiter on the beaches prior to their arctic fur seals make a series of feeding trips to sea, re- departure to sea. Comparison of weights among years turning to shore between each trip to suckle their pups gives an indication of the condition of chicks in relation for 1-2 days. The attendance of 40 lactating fur seals on to the relative abundance of prey in offshore foraging ar- the rookery beach is monitored continuously during this eas. Chick diet samples are obtained every 5 days by time via radio transmitters attached to the seals and an capturing and lavaging adults returning to the colony to automated radio reception/data-logging system. An at- feed their chicks. The food items regurgitated by the tempt is made to monitor instrumented female fur seals adults are preseIVed for detailed analyses of charac- for at least their first six feeding trips to sea. The radio teristics of prey fed to chicks. Krill is the major prey

October-November-December 1994 The main camp at NOAA' s research site at Seal Island, Antarctica, with chinstrap penguins and Weddell seal and an Antarctic fur seal (on the left). species evident from stomach lavaging at Seal Island. possible. The main objectives of pack-ice seal research However. evidence of fish prey is often present in diet are samples taken from birds returning from nocturnal feeding trips. For example, in 1992- 60% of the samples I. To suIVey pack-ice seal abundance and distribu- taken from nocturnal/early morning foragers (n = 15) tion, contained fish in addition to krill. In contrast, only 10% of the lavage samples taken from diurnal foragers (n = 2. To monitor crab eater seal habitat use and seasonal 20) had evidence offish. movements

Researchers monitor the duration of foraging trips of 3. To investigate seasonal changes in crabeater seal 40 chinstrap penguin adults fitted with radio transnlit- diving and feeding behavior ters to deternline the amount of time at sea required by breeding adults to meet the energetic needs for them- 4. To assess crnbeater seal haulout patterns selves and for their chicks. This research provides information on trends in trip duration both within and 5. To evaluate the genetic discreteness of pack-ice between various seasons. In addition, TDRs are de- seal populations ployed on 40-50 chinstrap penguins to obtain detailed information on their diving behavior and foraging effort 6. To compare evidence of the presence of various at sea. diseases in ice seals from different areas, and

Pack- Ice Seal Research 7. To deternline long-term reproductive and demographic patterns. Research in the sea-ice zone is conducted to comple- ment land-based studies at Seal Island. The principal fo- Satellite telemetry is successfully utilized to assess the seasonal movements cus for these investigations is crabeater seals (Lobodon , habitat use, foraging behavior and activity patterns of crabeater seals in the Weddell carcinophagus) and leopard seals, but complementary Sea and along the Antarctic Peninsula. studies on Weddell seals (Leptonychotes weddelli) and Data on the seals Ross seals (Ommatophoca rossii) are conducted when ' activity patterns, dive characteristics , and geo- AFSC Quarterly Report A colony of macaroni penguins at the North Cove study area. graphic location are relayed via the ARGOS system way, and Sweden) have been compiled over the past 25 aboard NOAA' s poiar-Olbiting satellites for up to 10 years into an integrated database at the WvIML. Infor- months to provide data on seasonal changes in seal be- mation on seals' reproductive status (reproductive havior and distribution. tracts) and age structure (teeth) has revealed inter- decadal changes in the status of crabeater seal popula- Aerial surveys for pack-ice seal abundance and dis- tions; analyses of this important database is continuing. tribution will be conducted in February and March 1995 as line transect suIVeys flown from helicopters operat- Program Support ing from aU. S. Coast Guard ice-breaker. Census obser- vations also will be made from the ship when aerial Research conducted through NMML ' s Antarctic Eco- suIVeys are not possible. Such suIVeys will be used to s Na- evaluate the extent to which ice type proximity to the systems Program has been supported by NOAA' tional Marine Fisheries Service as part of its Antarctic marginal sea-ice zone , and bathymetric features affect Marine Living Resources (AMLR) Program, which is pack-ice seal distribution. Data on seal haulout patterns adnlinistered by the Southwest Fisheries Science Cen- made possible by satellite telemetry will allow correct- ter. Following the conclusion of the 1994-95 field sea- ing estimates of seal abundance derived from aerial son, responsibility for the research on land-breeding counts~ haulout data allow estimating the proportion of pinnipeds and seabirds will be transferred to the South- seals that were not seen because they were not hauled west Fisheries Science Center. The National Science out on sea ice during the suIVeys. Foundation s Office of Polar Programs has also provided support, particularly for pack-ice seal research. Specimen material from scientific and commercial Early-season transportation of the Seal Island field team collections of crabeater seals provides an excellent to its research site has been provided by the Antarctic source of data on reproductive and demographic pat- tour operators Society Expeditions and Abercrombie terns. Data and specimens from a variety of sources and Kent. (the United States, the United Kingdom, Russia, Nor-

October-November- December 1994