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Euphausia superba Dana was collected at stations encompassing 3" of latitude in icecovered waters west of the Antarctic Peninsula in winter of 1992 (July-August), and in the same region the previous summer (December-January). There was no significant change in any biometric index (dry weight vs length, carbon vs dry weight, nitrogen vs dry weight, or body C:N). Rates of ammonium excretion in winter were not significantly different from those previously reported for E. superba in summer. It was clear that E. superba fed as a carnivore in winter. Copepod body parts consistently occurred in M 1 guts. During winter shipboard experiments, freshly caught krill ingested copepods and produced faeces at rates comparable to those measured in summer. The low ratio of N:P excretion (2.02) also suggests carnivorous feeding. A physiological model of carbon and nitrogen metabolism indicates that E. superba must feed during winter to maintain its observed C : N ratio and rate of ammonium excretion. On a diet of less than 1 Metridia gerlachei female copepod per day, a 20 mm knll can grow with a growth efficiency comparable to that achieved in summer. We suggest that starvation, body shrinkage and reduced metabohsm are unusual behaviors for knll in winter, and that carnivory sustains growth until ice algae become available as food in late winter and early spring.

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Euphausia superba and Thysanoessa macrura were the 2 most abundant euphausiids in the ice-covered waters west of the Antarctic Peninsula during July and August 1992. E. crystallorophias was limited to inshore waters. Detailed stratlfled sampling revealed that E. superba formed dense aggregations well below the ice, but was not inhabiting the ice itself In general, E. superba occupied the depth stratum from 15 to 130 m; few or no other zooplankton were found within E. superba swarms.7: rnacrura displayed a depth preference for the strata from 90 to 250 m. Size-frequency distributions for E. superba and for 7: rnacrura showed that larvae were absent and that both populations were dominated by small adults. A life cycle for 7: macrura is proposed.

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