RELATIONSHIP BETWEEN JUVENILE GROWTH AND THE ONSET OF SEXUAL MATURITYOF FEMALE NORTH-SEA PLAICE, PLEURONECTES-PLATESSA

The relationship between juvenile growth and the onset of sexual matur ation of female North Sea plaice, Pleuronectes platessa, is explored o n the individual and population level by analysing individual growth c urves back-calculated from otoliths of immature and mature fish and by analysing maturity-length ogives of individual cohorts sampled betwee n 1960 and 1990 from commercial landings from three areas in the North Sea. Back-calculated growth rate of females sampled as mature fish wa s higher than that of immature females up to 3 yr prior to sampling bu t lower in the last year. The probability of maturation was significan tly related to the length reached as well as to the growth rate in pre vious years. Maturity-length relationships from market samples showed significant differences in slopes and intercepts between age groups, g eographical areas, and year classes. Length at maturation (L(mat)) dec reased with age and increased with latitude. The differences in L(mat) of individual year-classes corresponded to differences in the growth rate and temperature during early life. Both the evidence obtained fro m the individual and population analysis suggest a 2- to 3-yr maturati on time. A model of the juvenile-adult transition process is proposed that provides a consistent interpretation of the observations.