Production and biochemical composition of eggs from neritic calanoid copepods reared in large outdoor tanks (Limfjord, Denmark)

Populations of Acartia tonsa (Dana) and Centropages hamatus (Lilljeborg) were monitored in outdoor enclosures imitating the natural estuarine environment in northern Denmark from August 2003 to February 2004. A. tonsa was predominant in summer while C. hamatus dominated from October and onwards. Mean egg production was normally higher in C. hamatus as compared to A. tonsa and continued until late December before a decrease was observed. Hatching success remained high even in February at temperatures below zero degree indicating that no diapause eggs were produced. Further, the egg quality evaluated from the fatty acids (AA, EPA and DHA) and amino acid contents did not change markedly during the study period. From this observation it is strongly suggested that nauplii originated from copepod eggs produced throughout the monitored sampling period constitute an adequate live feed for fish larvae probably even year round.