Seasonal observations on moulting and maturation in Stage V copepodites of Calanus finmarchicus from the Firth of Clyde

Stage V copepodites of Calarms finmarchicus collected from the Firth of Clyde during April–August 1978 and October 1979–January 1980 moulted to adults in the laboratory. The interval between capture and ecdysis was longer on average and less variable during the months July–November (when overwintering stocks build up in the Firth) than April–June. Overwintering Stage V copepodites moulted earlier in the laboratory than in the sea; this is not associated with differences in environmental factors known to affect developmental rate and may have been induced by stress associated with capture or handling. A similar induction of moulting is not evident in spring and summer generations.