MANAGEMENT OF EVOLVING FISH STOCKS

Mortality caused by harvesting can select for life history changes in the harvested stock. Should this possibility be taken into account in the management of renewable resources? I compare the performance of di fferent harvest strategies when evolutionary change is accounted for w ith the help of an age-structured population dynamics model. Assuming that age of first reproduction is the only evolving trait, harvesting of only mature individuals selects for delayed maturation and results in increased sustainable yields. Unselective harvesting of both mature and immature fish selects for earlier maturation which causes the sus tainable yield to decrease. Constant stock size and constant harvest r ate strategies perform equally well in terms of maximum sustainable yi eld, both before and after evolutionary change. The maximum sustainabl e yield for fixed-quota strategies is lower. All those strategies have similar evolutionary consequences given a similar average harvest rat e. Coevolutionary dynamics between fish stock and the stock manager in dicate that the evolutionary benefits of selective harvesting are atta inable without incurring yield losses in the near future.