On the Recruitment of O-Group Plaice in the North Sea

(i) Variability in North Sea plaice recruitment seems to be generated mainly during the egg stage. (ii) Density-dependent mortality processes, if they apply, are likely to operate in the early post-larval stage in the nurseries. However, the data do not exclude the possiblity that such processes are lacking or insignificant in juvenile plaice. (iii) An inverse relationship between length and abundance, observed in O-group plaice, appears to be generated by temperature-dependent processes in the egg stage, affecting the rate of egg development and egg mortality. (iv) Recruitment fluctuations in North Sea plaice are probably mainly generated by between-year temperature differences experienced during the egg stage. Variations in egg production by the adult stock might also affect recruitment, but in the range of stock sizes considered the effect seems less important.