Exploiting natural populations in an uncertain world

摘要: Abstract We consider some aspects of the way random environmental variability can affect fish and other natural populations that are being harvested for sustained yield. A spectrum 8 stock-recruitment curves, culled from fisheries literature, is used to study probability distribution yield Y as a function level exploitation or “effort” E. If noise enters via intrinsic growth rates (“density-independent noise”), curves qualitatively in accord predicting absolute levels fluctuation increase E increases; these trends become strongly marked once significantly excess maximum (MSY) level. The quantitative details, however, depend on specifics curve (the CV relative decrease increases toward neighborhood MSY level, relatively dramatically gradually beyond this level). effects density dependent noise, time delays population regulatory processes, also briefly discussed. Broadly, analysis suggests unpredictability pose “portfolio theory” trade-offs between desired average fluctuations risk. What seems really needed not further mathematical refinement, but rather robustly self-correcting strategies operate with only fuzzy knowledge about stock recruitment curves.