A SIMPLIFIED FORMULATION FOR FISH PRODUCTION

A new formulation for fish production is presented, one that clearly e mbodies the balance between aggregate somatic growth and losses due to natural and fishing mortality. The method permits simplified calculat ion of production over biomass and yield over production ratios; estim ates of the latter can be used to investigate the reliability of yield as a proxy for production. Simple applications of the formulation ind icate taxonomic variation in the yield to production ratio. Specifical ly, production is well approximated by yield for many piscivorous spec ies, but yield seriously underestimates production for prey species.