Distribution, biomass and abundance of Antarctic krill in the vicinity of Elephant Island during the 1996 austral summer

Results from two acoustic and net surveys conducted in the vicinity of Elephant Island during the 1996 austral summer indicate very good krill recruitment from spawning in 1994/5. Areas of high krill density were mapped north of King George and Elephant Islands where water depth was greater than 200m. One-year old juvenile krill numerically dominated catches during the first survey in January and were widely distributed throughout the southern portion of the survey area. Large, sexually mature adult krill were caught during both surveys north of the islands, but were numerically dominate only during the second survey in February-March. Intermediate size krill were caught in very low numbers reflecting poor recruitment from spawning in 1992/93, and 1993/94. Biomass and abundance estimates were the highest since 1992 when the effect of good recruitment from spawning in 1991 was observed. The abundance of salps was similar to 1995 and two to three orders of magnitude less than observed in 1993 and 1994. Following three winters of relatively low sea ice cover off the western side of the Antarctic Peninsula, the winter of 1994 marked the beginning of a period of relatively extensive ice coverage continuing through 1995. These observations support the hypothesized relationships between winter sea ice conditions, the lack of a spring-time salp bloom, the timing of spawning by adult krill, and the success of krill recruitment proposed by Loeb and Siegel (1994a) and Siegel and Loeb (1995).