The 2008-2009 U.S. Antarctic Marine Living Resources (U.S. AMLR) Survey, conducted by the Antarctic Ecosystem Research Division (AERD), represents the 23rd annual survey conducted in the South Shetland Islands region of Antarctica. The data collected complement a long-term dataset that is critical to national and international management committees such as the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). Due to recent, rapid and pervasive ecosystem changes owing to climate, the AMLR Survey is also important to the detection of climate change and its effects on international fisheries.
This year two field stations were operated from October through March, during breeding period of land-based Antarctic predators at Cape Shirreff, on Livingston Island, and Admiralty Bay (Copacabana), on King George Island. In addition, two ship-based surveys were conducted: one survey of pelagic (open-water) zooplankton, seabirds and marine mammals was conducted around the South Shetland Islands; a second survey of finfish and benthic invertebrates was conducted around the South Orkney and South Shetland Islands.
Cape Shirreff field station
Pinniped, penguin and skua population monitoring
AERD scientists opened the Cape Shirreff field station on October 24, 2008 and closed it on March 7, 2009. During the months that the station was open, scientists studied breeding populations of Antarctic fur seals (AFS), gentoo penguins, chinstrap penguins and skuas, as well as leopard seals and Southern elephant seals (SES) that were present at the Cape.
Fur seal births occurred earlier this year than any year since the start of monitoring at Cape Shirreff in 1997/98. The median date of births was December 5, 2008. Pup production declined by 13.3% compared to the previous year, and the total number of pups counted on the U.S. AMLR study site was 1,547 (s.d. = 4.6). Leopard seal numbers at Cape Shirreff appear to be increasing along with predation on fur seal pups. This year 25 tagged leopard seals returned to Cape Shirreff, and several untagged leopard seals were also seen in the area. We successfully deployed a time depth recorder that had recorded over a month of leopard seal diving behavior.
A total of 4,332 chinstrap penguin chicks hatched this year at the U.S. AMLR study site on Cape Shirreff. Of those, 128 died.
Copacabana field station
Penguin and skua population monitoring
In cooperation with the National Science Foundation (NSF), the AERD maintained their annual field operations at Copacabana on King George Island from October 19, 2008 though March 8, 2009. During that time, scientists monitored the local breeding colonies of gentoo, Adélie and chinstrap penguins, as well as skuas. They also took a regular census of fur seals, and monitored leopard seal and elephant seal presence on the island.
This year, for the first time in the history of AERD and Copacabana, researchers spotted a 20-year-old gentoo penguin – the oldest known penguin to return to Copacabana. The penguin had been tagged as a chick during the 1988-1989 breeding season. Another highlight of the season was the first completely melanistic (black) Adélie penguin ever recorded at Copacabana.
The breeding season was strong for gentoo, chinstrap and Adélie penguins. Each species had more chicks this year than last year. However, skuas did not fare as well: from 108 breeding pairs, only 19 skua chicks survived to the end of the breeding season.
Ship-based survey: Leg I
Antarctic krill stock assessment; zooplankton, seabird and marine mammal monitoring
The annual ship-based U.S. AMLR survey started on January 8, 2009. Leg I of the cruise lasted 26 days, during which scientists from the AERD described krill abundance and distribution, zooplankton community structure, and seabird and marine mammal distribution and abundance in the South Shetlands Islands.
Strong south eastward blowing winds brought warmer, moist air masses to the Peninsula region throughout most of the summer. Although primary productivity was equal to or greater than previous years, the surface waters in the ACC were more deeply mixed. Krill biomass in the South Shetland Islands was similar to that observed in 2008 and less than in 2007. Recruitment of krill was lower than in the previous two years, and krill were largely two and three years old.
Seabird and marine mammal distributions also reflected the influence of the warm ACC waters. Many birds that prefer warmer waters than normally found in the Southern Ocean, such as prions and white-chinned petrels, were found in larger numbers this year than in previous years. At the same time, fin whales were found in larger numbers and more widely distributed than has been previously recorded during the U.S. AMLR survey.
Ship-based survey: Leg II
Antarctic finfish stock assessment; pelagic fish, zooplankton and benthic invertebrate monitoring
Leg II of the U.S. AMLR survey was a 35 day cruise, conducted in the South Orkney and South Shetland Islands during February and March of 2009. This survey focused on stock assessment of finfish populations that have been compromised by previously un-managed fisheries, as well as the identification of Vulnerable Marine Ecosystems (VME) – ecosystems at the sea floor with a diversity of species that are found in very few places in the world.
The deployment of an underwater camera/video configuration allowed for the discovery of several possible VMEs in the South Orkney Islands and north of the Antarctic Peninsula, where a diverse community of demosponges and hexactinellid glass sponges, as well as bamboo corals and byrozoan reefs make their home.
The AERD collected 62 species of finfish, two of which have never before been described; their description will be delegated to Yale University. One species in particular, a finfish that was hunted nearly to extinction before the Antarctic fishery was managed, was found to be slowly recovering, especially near the Weddell Sea. The information gathered during this cruise will be used to characterize the distribution and demography of finfish species, and advise CCAMLR on the potential for re-opening the finfish fishery north of the Antarctic Peninsula.
During the cruise scientists also collected oceanographic data, such as current speed and direction, water temperature and salinity, and weather, to describe the links between the physical processes occurring in the ocean and distribution of benthic invertebrates and finfish.
- 1765 Adélie penguin chicks counted
- 250 Adélie penguin chicks banded
- 6 Adélie penguins tagged
- 100 Adélie fledglings weighed