Dynamics of Exploited Marine Fish Populations

Abstract

In the exploitation of marine fish populations, it is necessary to track the effects of fisheries to ensure sustainable use of the natural resource and security of the resource into the future. Population models and statistics are used to assess the status of exploited fish stocks, termed stock assessment models. Three common stock assessment models include surplus production models, virtual population analysis, and statistical catch-at-age models. These models are used to generate (1) estimates of annual spawning stock biomass and fishing mortality rate experienced by the stock, and (2) biological references points of these metrics. Biological reference points allow the comparison of current estimates of biomass and mortality to target or threshold levels. These comparisons allow stock assessment scientists to gauge whether overfishing is occurring and if the stock is overfished. Sometimes the effects of overfishing go beyond reductions in yield and biomass, leaving the stock depleted in age structure, size structure, growth rate, or reproductive output. Since it is difficult to experiment on the effects of various management strategies on the recovery of a stock, or on the reliability of assessment model output, management strategy evaluation can be used to generate a simulated population based on empirical data and test hypotheses related to management strategies. Therefore, management strategy evaluation is a valuable tool in the arsenal of a stock assessment scientist to ensure appropriate assessment and management of exploited marine fish populations.