Effect of starvation on the reproductive potential of Calanus finmarchicus

The effect of starvation on gonad morphology and egg production of Calanus finmarchicus uas studied during the winter spring transition in a North Nor wegian fjord. Single females were exposed either to surplus food or to filt ered seawater for 4-9 d in short-term experiments and for 3 weeks in long-t erm experiments. Additional laboratory experiments were performed with fema le C. finmarchicus from the Norwegian Sea, studying the resumption of egg p roduction after short (1-3 d) or long (15 d) intervals of starvation. In fe d females, gonads Here mature and rates of egg production were relatively h igh. During starvation, gonads remained immature or returned to an immature stage: no eggs were produced. Histological analysis of starving females sh owed that oocytes in the diverticula disintegrated, while cells in the ovar y were intact. After two weeks of starvation, reproductive activity resumed within a week of surplus feeding. However, egg production remained signifi cantly lower than in females fed continuously. When female C. finmarchicus were exposed to short starvation intervals, reproduction decreased signific antly owing to both higher percentages of non-spawning females and decreasi ng clutch sizes. The experiments have shown that starvation periods have a strong influence on reproduction of C. finmarchicus, which was dependent on the duration of starvation and the timing within the maturation cycle. Lif etime fecundity is probably considerably reduced, obviously during starvati on but also as a result of long-term effects. (C) 2000 International Counci l for the Exploration of the Sea.