Observations of krill from ice camps during two winter cruises, August 2001 and August/September 2002,

west of the Antarctic Peninsula

L.B. Quetin, R.M. Ross, C. Boch, S. Dovell, E. Hessell, K. Johnston, S. Oakes, and A. Willis

Marine Science Institute, University of California at Santa Barbara, Santa Barbara, CA 93106

During two winter cruises to the Southern Ocean GLOBEC study region west of the Antarctic Peninsula between 66.3° and 68.5°S, five ice camps were occupied for periods of 3 to 8 d. Observations by SCUBA divers in the under-ice habitat showed both interannual and site-specific variation in the location and behavior of Antarctic krill. The strength of the attachment to the under-ice surface varied between the two years. During August 2001, larval krill were always seen coupled to the under-ice surface and feeding on ‘floors’ in over-rafted areas, but during the August/September 2002 cruise the degree of attachment varied with the location of the ice camp. During the August/September 2002 cruise, the numbers and degree of coupling of larval krill to the under-ice surface increased from Ice Camp Sparky, the southernmost camp, to Ice Camp Pisco, the northmost camp. At Ice Camp Rodin, where few larvae were coupled to the under-ice surface, tows from drifting ice floes with paired nets at 1 m and 10 m below the ice surface were used to compare the day/night behavior of larval krill. The catches differed both day to night and at the two depths. Ice Camp Rodin was also the only location where adult krill were seen by divers. They were in the water column, swimming in schools 15 – 20 ft below the ice with the ice drifting over them.