A versatile new stock-recruitment relationship for fisheries, and the construction of sustainable yield curves

Abstract

A versatile functional form relating recruitment to spawning stock biomass for fisheries is proposed. The non-negative, three-parameter form distinguishes resilience and degree of compensation as two aspects of the density dependence of recruitment, and permits the representation of non-asymptotic, asymptotic, and domed stock-recruitment relationships by parameter variation within the same functional form. Simple methods for parameter estimation are discussed. A method is given for combining the relationship proposed with yield-per-recruit and biomass-per-recruit estimates obtained by any conventional method, in order to construct the yield curves relating total yield to biomass or fishing mortality. These yield curves may be used in a fashion similar to those obtained from general production models, but include explicitly the effects of actual growth (weight at age), and maturity data, and of actual exploitation patterns. They are therefore particularly useful for selecting target values for fishing mortality and minimum values for spawning biomass, and for estimating long-term sustainable yields in a moderately conservative fashion.