A GENERALIZED STOCK-RECRUITMENT RELATIONSHIP FITTED TO THE OBSERVED YIELD - IMPLICATIONS FOR THE RECRUITMENT DYNAMIC

The present study presents a method of assessing and fitting a stock-r ecruitment relationship. The method is based on a combination of an eq uilibrium production model and a yield per recruit model. Tt does not use recruitment data which are, in general, highly dispersed, but prod uction data. Thus, the relationship obtained is not of the parametric form of classical stock-recruitment relationship such as those of the Beverton and Holt (1957) and Ricker (1954), however, in some cases, th e resulting stock-recruitment curve resembles models currently used in fisheries science. It is interpreted as an expectation of the recruit ment conditionally to stock spawning biomass and stock demographic str ucture. However, for some realistic values of the parameters, the curv e thus obtained describes a loop which suggests that two different rec ruitment levels may be expected from the same stock spawning biomass l evel. This theoretical property is illustrated with simulations. As an illustrative example, the method is applied to North-West Atlantic ga doid stocks. The significance of the method, its originality, the vali dity of the underlying assumptions and their conceptual consequences a re discussed.