Egg production of Calanus finmarchicus—A basin-scale study

Abstract

Egg production of Calanus finmarchicus was studied during joint basin-scale surveys in April-June 2003 in the Norwegian Sea. Surveys covered the whole Norwegian Sea and were conducted from Norwegian, Icelandic and Faroese research vessels. Stations were classified as being in pre-bloom, bloom or post-bloom phase according to levels of chlorophyll a and nitrate. Individual egg production rates and population egg production rates were calculated and compared between areas. Both individual egg production rates (eggs female -1 day -1 ) and population egg production rates (eggs m -2 day -1 ) were significantly higher in bloom areas compared with pre-bloom and post-bloom areas. However, when integrated over an estimated duration of the three phases, the time-integrated egg production (eggs m -2 ) in most years was highest in the pre-bloom phase, and this was explained by the longer duration of this phase compared with the two other phases.