Fish Population Dynamic and Stock Assessment

1.4.2. Stock assessment

It is the process of collecting and analyzing demographic information about fish populations to describe the conditions or status of a fish stock. The result of a stock assessment is a report that often includes an estimation of the amount or abundance of the resource, an estimation of the rate at which it is being removed due to harvesting and other causes, and one or more reference levels of harvesting rate and/or abundance at which the stock can maintain itself in the long term. Stock assessment often contain short-term (1-5 years, typically) projections or prognoses for the stock under a number of different scenarios. This information on resource status is used by managers to determine what actions are needed to promote the best use of our living marine resources.

Stock assessment reports describe a range of life history characteristics for a given species, including age, growth, natural mortality, sexual maturity and reproduction, stock boundaries, diet preferences, habitat characteristics, species interactions, and environmental factors that may affect the species. Assessment reports also include descriptions of the fishery for a species, using information from both scientists and fishermen. Additionally, stock assessments describe the assessment model, or the collection of mathematical and statistical techniques that were used to perform the stock assessment.

Stock assessment analyses rely on various sources of information to estimate resource abundance and population trends. The principal information comes from the commercial and recreational fisheries ( fishery-dependent information ). For example, the quantity of fish caught and the individual sizes of the fish, their biological characteristics (e.g. age, maturity, and sex), and the ratio of fish caught to the time spent for fishing (catch per unit of effort) are basic data for stock assessments.

Understanding the natural history of the harvested species and the other species with which they interact is crucial to understanding the population dynamics of living marine resources.