A New Concept of the Stock-Recruitment Relationship for the Japanese Sardine, Sardinops Melanostictus

The aim of this paper is to discuss the validity of the results of Wada and Jacobson (Can. J. Fish. Aquat. Sci. 55, 1998) and to propose a new concept of the stock-recruitment relationship for the Japanese sardine. Two regression analyses were used: simple regression and Deming regression. Reproductive success was defined as recruitment (R) divided by egg production. A false decreasing trend was produced in the regression line of ln(reproductive success) against ln(egg production) in response to observation error. When Deming regression was applied, the slope of the regression line of ln(R) against ln(egg production) did not statistically differ from unity. This indicates that a density-dependent effect cannot be detected on the stock-recruitment relationship in the data used in this study and that it is reasonable instead to accept a proportional model as the optimal stock-recruitment relationship model for the Japanese sardine. The results of this study are diametrically opposed to those of Wada and Jacobson (1998), who assumed that density-dependent effects on recruitment typically exist for Sardinops species.