The Dependence of Recruitment on Parent Stock in Different Groups of Fishes

An attempt was made to establish differences between groups of fishes in the nature of their stock and recruitment curves. Recruitment in logarithms was plotted on stock in logarithms and the slope was used as an index of density dependence. A number of stocks of Pacific salmon, Atlantic herring, Pacific herring, flatfish and gadoids were examined. It was found that the index of density dependence was inversely correlated with the cube root of the fecundity, which implies that for stocks of the same size, the distance apart of the larvae plays animportant part in the determination of density dependence. Four pelagic stocks, Hokkaido herring, Norwegian herring, Japanese sardine and Californian sardine, were examined. The stocks collapsed when fishing effort was high, and it was suggested that in two cases RICKER'S limiting value of the exploitation rate might have been reached.