Relationship between Juvenile Growth and the Onset of Sexual Maturity of Female North Sea Plaice,Pleuronectes platessa

Abstract

The relationship between juvenile growth and the onset of sexual maturation of female North Sea plaice, Pleuronectes platessa, is explored on the individual and population level by analysing individual growth curves back-calculated from otoliths of immature and mature fish and by analysing maturity–length ogives of individual cohorts sampled between 1960 and 1990 from commercial landings from three areas in the North Sea. Back-calculated growth rate of females sampled as mature fish was higher than that of immature females up to 3 yr prior to sampling but lower in the last year. The probability of maturation was significantly related to the length reached as well as to the growth rate in previous years. Maturity–length relationships from market samples showed significant differences in slopes and intercepts between age groups, geographical areas, and year classes. Length at maturation (Lmat) decreased with age and increased with latitude. The differences in Lmatof individual year-classes corresponded to differences in the growth rate and temperature during early life. Both the evidence obtained from the individual and population analysis suggest a 2- to 3-yr maturation time. A model of the juvenile–adult transition process is proposed that provides a consistent interpretation of the observations.