Copepod egg production in the Skagerrak during SKAGEX,May–June 1990

Egg production ofAcartia clausi andCentropages hamatus was measured along 6 transects in the Skagerrak every third day from 26 May to 20 June 1990. Egg production was highest in the shallow waters north of Denmark, with occasional peaks in frontal regions along the Swedish and the Danish west coasts. Linear regression analysis showed that the egg production was significantly (p<0.05) related to chlorophylla measured either as average surface concentration or integrated over the whole water column. When analysing each transect or each time period separately, the surface chlorophyll generally was a better predictor of egg production than the depth-integrated chlorophyll. Regressions improved when analysing the whole area for a short period of time rather than analysing a single transect for a month. The data suggest that the Skagerrak planktonic system functions more similarly over the whole area in a short period of time than over a month in a restricted area. Mixingwithin the system in frontal regions or in connection with eddies is more important for the secondary production thantransport to it by the Baltic Current or the Jutland Current.SKAGEX Contribution No. 4