Colonization and Reintroduction of Anadromous Salmonids

Human activity over the past centuries has precipitated not only the widespread reduction in abundance of individual anadromous salmonid populations, but the outright extirpation of many of them.  Fisheries management agencies are actively involved in developing recovery plans to rebuild salmon.  Opportunities for re-establishing extinct populations have generally been associated with dam removal events, or with construction of new passage structures to permit upstream and downstream migration.  In these cases, the goal of the plans is to recreate naturally self-sustaining populations, typically by permitting natural recolonization or by actively reintroducing fish.  However, numerous questions exist regarding what management approach is most appropriate. Should a passive approach be adopted, allowing native fish to naturally migrate into and colonize a reopened habitat?  Should wild fish - native or from a nearby population - be captured and actively reintroduced?  Should reintroduction be facilitated through successive years of supplementation with hatchery-reared fish?

A number of presentations have already been solicited to describe programs in both the Atlantic and the Pacific basins, involved in recreating extirpated salmonid populations.  Several will review examples where fish have been permitted to naturally colonize reopened habitats, as well as a few where non-native fish have “invaded” new habitats.  The primary objective is to gain insight into what are the dominant habitat factors and natural processes associated with successful establishment of a new salmonid population.  Additional presentations will describe efforts where extirpated populations have been actively reintroduced and rebuilt through hatchery supplementation.  These will provide insight on the conditions under which particular hatchery management methodologies lead to successful re-naturalization of the fish, including choice of source stock, broodstock selection, spawning and juvenile rearing, and acclimation and release procedures.