Integrated Hatchery and Population Management Strategies for Effective Fisheries Enhancement and Restoration

Hatchery-based enhancement and restoration programs may be developed in a variety of fisheries situations and with a view to achieving different goals. Different situations and goals may call for very different combinations of hatchery practices, release and fishing regimes. For example, ranching systems operate for species that do not recruit naturally and may be managed to maximize biomass production or the abundance of catchable-sized fish, often manipulating populations in ways that could not be achieved in naturally recruiting populations. Because direct genetic interactions with wild stocks are absent, post-release fitness of cultured fish is primarily an economic rather than a conservation issue and such fisheries may even benefit from selective breeding to enhance return rates. Stock enhancement on the other hand involves the continued release of hatchery fish into a self-recruiting wild population, with the aim of sustaining and improving fisheries in the face of intensive exploitation and/or habitat degradation. Enhancement through release of advanced juveniles may increase total yield and stock abundance, but is likely to reduce abundance of the naturally recruited stock component through compensatory responses or overfishing. I discuss alternative enhancement system designs in the light of strategies for dealing with domestication issues and stock management.