Pretty Good Yield and exploited fishes

While much of traditional fisheries theory has concentrated on maximum or optimum yield, the reality of fisheries management is that biomass yield is only one of the several indicators of fisheries performance, and desired outcomes generally only need to provide something near the maximum possible yield. A range of policies are explored to find those that produce Pretty Good Yield defined as sustainable yield at least 80% of the maximum sustainable yield. Such yields are generally obtained over a broad range of stock sizes (20-50% of unfished stock abundance), and this range is not sensitive to the population's basic life history parameters such as natural mortality rate, somatic growth rate, or age at maturity. The most important biological parameter determining this range is the intensity of recruitment compensation. Meta-analysis shows compensation is usually strong and there is reasonably little yield lost at what are now widely accepted definitions of overfishing or risk for most stocks. Similarly, maintaining stocks at 50% of unfished stock abundance for ecological or economic reasons results in little expected loss of yield. (C) 2009 Elsevier Ltd. All rights reserved.