Variability of Fishing Mortality by Age: Consequences for Maximum Sustainable Yield

Abstract

Abstract The influence of variation in age-specific vulnerability to fishing on maximum sustainable yield (MSY) in numbers and weight was evaluated with simulation techniques that incorporated biological characteristics of red snapper Lutjanus campechanus and an arbitrary stock–recruitment relation. I evaluated MSY for 10 arbitrary selectivity ogives that systematically varied from greater vulnerability to fishing mortality among the oldest ages to greater vulnerability among the youngest ages. The values of MSY in numbers and weight varied by factors of 2.6 and 4.5, respectively, for the range of selectivity schedules examined. Because selectivity schedules often are not constant through time, values estimated from catch data should be viewed with caution when they are applied in current management settings. Further, setting MSY as a management objective will often be insufficient for developing management advice unless the desired longterm age composition of the catch or some other qualifying factor is ...