Jeffrey A. Hutchings

Killam Memorial Chair, Dalhousie University, Canada

Evolutionary Ecology & Life History Evolution of Fishes

Recovery and Extinction Probabilities of Species at Risk: Synopsis

Although some species have responded favourably to reductions in fishing mortality, many severely depleted populations have not, rendering them, or their constituent populations, at increased risk of extinction.  What are the primary correlates of recovery?  What distinguishes populations which appear to recover rapidly from collapse from those that do not?  Foremost among potential factors is the degree to which fishing mortality is reduced.  Another key consideration is the suite of life history traits expressed by the population in question.  Changes to species communities, assemblages, and food webs can also influence recovery by altering inter-specific predation and competition.   Under some circumstances, habitat modification, effected primarily by bottom-deployed fishing gear, might also affect recovery.  There is also reason to hypothesize that recovery potential may decline dramatically once abundance has fallen below some threshold.  Such a phenomenon -- variously termed the Allee Effect, positive density-dependence, or depensation -- can be driven by peculiarities associated with a species’ mating system or by the responses of predators to changes in the relative abundance of their prey.  In addition to the efficacy of various management and societal responses to fish population collapses, research into the factors influencing recovery should also be cognizant of the evolutionary or genetic responses by fish populations to the intensive levels of mortality that fishing can impose on affected populations.