Krill, salps and other dominant zooplankton taxa in the Elephant Island area during the 1997 austral summer

Results from two net surveys in the Elephant Island area during January-March indicated moderate krill abundance and lower recruitment success of the 1995/96 year class relative to that of 1994/95. These occurred after a relatively early 1996 spawning season that theoretically should have promoted good krill recruitment. However winter 1996 was characterized by slightly below average winter 1996 sea-ice conditions. These observations strongly suggest that winter sea-ice extent greatly affects larval survival and recruitment even when krill spawning is relatively early. Salp abundance values during March Survey D were second only to those observed during February-March 1993 and, like 1993, resulted from massive population growth during summer. This bloom, as those in previous "salp years", followed a winter with relatively low sea-ice development. The other zooplankton collected included a diverse taxonomic assemblage. Copepods, salps, and postlarval Thysanoessa macrura were the numerical dominants during both surveys. Day-night catch differences and interspecific relationships among various zooplankton taxa observed during January-February Survey A are described here.