Feeding and energy budgets of Antarctic krill Euphausia superba at the onset of winter—II. Juveniles and adults

• DOI: 10.4319/lo.2002.47.4.0953
• Publication Date: 2010-06-30T20:24:52Z
• Authors: A. Atkinson; B. Meyer; D. Stuϋbing; W. Hagen; K. Schmidt; U. V. Bathmann
• Keywords: Antarctic krill; Detritus; Calanus; Clearance rate; Diel vertical migration; Overwintering

The overwintering success of Euphausia superba is a key factor that dictates population size, but there uncertainty over how they cope with the scarcity pelagic food. Both nonfeeding strategies (reduced metabolism, lipid use, or shrinkage in size) and switching to other foods (carnivory, ice algae, detritus) have been suggested. We examined these alternatives southwest Lazarev Sea autumn (April 1999), when sea was forming phytoplankton at winter concentrations. juveniles adults had very high content (36% 44% dry mass, respectively) which >40% phospholipid. However, their low O:N ratios suggested reserves were not being used. Results from gut contents analysis large volume incubations agreed fed mainly on small (<3 mm) copepods. This dietary difference supported possibly by elevated concentrations 20 : 1 22 fatty acids adults. feeding methods also confirmed rates compared those summer. Even acclimated food concentrations, clearance ingestion <30% summer rates. Respiration ammonium excretion freshly caught krill 60%–80% declined significantly during 18 d starvation. These findings suggest both switch energy conservation strategies, trend reduced more carnivorous ontogeny. points “compromise” strategy for postlarvae, are alternative explanations. First, may an transition mode, and, second, some maintained effort whereas remainder feeding.