Reproductive Variability in North Sea Cod, Plaice and Sole

摘要

The between year variability in reproductive effort of the parent stock of North Sea plaice, sole and cod is investigated using time series of growth, maturation and fecundity. Special attention is given to the possible density dependent effects. Time trends were observed in growth rate and maturation of plaice, growth rate, maturation and gonad weight of sole and in maturation and fecundity of cod. In both plaice and sole the growth rate increased in the 1960s. Density dependent growth in juvenile, pre-mature and adult growth could not be detected with the exception of somatic growth in 1- and 2-group plaice. In these cases however the relations could also be artificial due to the time trends. Variability in maturation and fecundity was studied in relation with variations in growth. Variability in age at first maturity was related with variability in growth of premature fish, but variability in length at first maturity could not be related to variability in growth. Variability in fecundity showed a weak positive relation with growth.