Methods for Evaluating the Impacts of Fisheries on North Atlantic Ecosystems
How Life History Patterns and Depth Zone Analysis Can Help Fisheries Policy
Dirk Zeller and Daniel Pauly
Fisheries Centre, University of British ColumbiaAbstract
The life-history patterns of fish species are complex. But much of this complexity can be captured in simple diagrams of coastal transects, where juveniles usually occur in larger numbers in shallow waters, while adults generally inhabit deeper, offshore waters. Such coastal transects can be used to show how different fisheries sectors (e.g. small versus large scale) may exploit different parts of the life history of the same species or stock. Thus, a species may ‘connect’ small with large scale fishery sectors through their life history patterns. We show how this can be visualized through iconographic representations of generalized life history patterns and depth profiles, with specific key life-history parameters. Relevant patterns include spawning areas, nursery/juvenile distributions, adult distributions and spawning migrations. Four preliminary case studies presented here illustrate some general patterns with regard to water depth and distance from shore. The diagrams allow us to incorporate into management the concept of life history interconnectivity between different fishery sectors. This contributes to sustainable ecosystem-based approaches by informing policy options when faced with decisions to rationalize overcapitalized fisheries.