JANE E. MARTIN, ROGER P. HEWITT, and RENNIE S. HOLT, Antarctic Ecosystem Research Group, Southwest Fisheries Science Center, La Jolla, California 92038
The U.S. Antarctic Marine Living Resources (AMLR) program has developed and conducted a research plan tailored to the goals of the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR), part of the Antarctic Treaty System. The Convention manages antarctic fisheries to conserve targeted species while also taking into account the impact fishing activities might have on other living organisms in the antarctic ecosystem. CCAMLR's unique management regime has come to be known as the "ecosystem approach." In keeping with CCAMLR's mandate, the impact of the krill ( Euphausia superba ) fishery upon dependent predators must be understood.
The AMLR program monitors finfish and krill fisheries, projects sustainable yields where possible, and formulates management advice and options. In addition, the program conducts field research with the long-term objective of describing the functional relationships between krill, their predators, and their environment. The field program is based on two working hypotheses:
In the previous eight seasons, the AMLR field program included a research cruise near Elephant, Clarence, and King George Islands, which are among the South Shetland Islands at the tip of the Antarctic Peninsula. Land-based studies were conducted at a field camp on Seal Island, off the northwest coast of Elephant Island. Because Seal Island was found to be unsafe due to landslide hazards, however, research at the camp was curtailed. Beginning this season, the AMLR study area was expanded to include a larger area around the South Shetland Islands, and a new field camp was established at Cape Shirreff, Livingston Island (figure 1). As in the past, research was also conducted at Palmer Station, a U.S. station on Anvers Island farther south on the Peninsula.
The specific objectives of the 1996-1997 field season were the following:
The cruise was conducted aboard the chartered research vessel (R/V) Yuzhmorgeologiya . Because of a delay in the arrival of AMLR cargo, the ship departed Punta Arenas, Chile, for Leg I on 19 January 1997, 4 days later than originally planned. Despite the delay, all original objectives were achieved and the leg was completed on 14 February. Following Leg I, the ship was delayed 23 days in Punta Arenas due to a failure of the main engine. After repairs were completed, Leg II was conducted 13-26 March with an abbreviated research plan.
During Leg I, a large-area survey of 106 conductivity-temperature-depth (CTD)/carousel and net sampling stations, separated by acoustic transects, was conducted in the expanded AMLR study area (Survey A, figure 2). Acoustic data were collected at three frequencies using 38-, 120-, and 200-kilohertz transducers. Data for physical oceanography, primary productivity, and krill distribution and condition studies were collected during the survey. Operations at each station included the following:
During Leg II, 16 CTD/IKMT stations, separated by acoustic transects, were conducted around Elephant Island (Survey D, figure 3). Operations at each station included the following:
Also during Leg II, seven bottom trawls were conducted at stations northwest of Robert and Nelson Islands, and west of Elephant Island.
A field team occupied the new camp at Cape Shirreff from 25 January to 8 March 1997. Approximately 100 Zodiac loads of building materials were transferred to the camp for the construction of four structures. The team also initiated abundance and growth studies on seabirds and assisted Chilean colleagues with antarctic fur seal research. Seal Island was occupied by a field team from 11 February to 16 March, which was longer than originally planned due to the ship delay. The team dismantled various camp structures for removal from the island, and conducted limited studies on penguins and antarctic fur seals. Fieldwork at Palmer Station was initiated on 28 September 1996 and completed on 15 April 1997; studies on aspects of the ecology of Adélie penguins were conducted.