A Conceptual Genetic Fitness Model for Fisheries Management

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Abstract
A generalized model for managing fisheries to maintain reproductive fitness is proposed. The fitness of an individual within a stock is its number of successful progeny, where successful means survival to the reproductive stage. The fitness of a stock is a probability distribution (W) described by its mean [Formula: see text] and variance (Vw). An example of equations, derived from a variance effective number, expresses the distribution as a function of phenotypic variables (including abundance, immigration and age structure) which could be estimated in fishery surveys. Management of a stock as a self-perpetuating system requires maintenance of its probability distribution at a sufficiently broad level, estimated from reference generations, to allow it to perpetuate in the face of fishing and natural mortality in a changing environment. Modification of the distribution by exploitation or management actions imposes the risk of reduction of genotypic diversity in the stock. Selection of appropriate reference generations requires careful attention to biological detail. Application of the model is illustrated by computing the effective number for fictitious stocks with different life histories.