Stock delineation of migratory and resident Pacific hake in Canadian waters

Within Canadian waters there are two distinct stocks of Pacific hake (Merluccius productus); an inshore resident stock and an offshore, migratory stock. From 2006 to 2008, a change in the migratory behavior of the offshore stock resulted in a shift of the entire fishery from the typical grounds off the west coast of Vancouver Island to the more northerly region of Queen Charlotte Sound. Management concerns regarding the unknown exploitation of any resident stocks prompted a re-examination of Pacific hake stock structure in Canadian waters. Population genetic techniques determined a connectivity of Pacific hake found in Queen Charlotte Sound in the summer to (1) the offshore migratory population; (2) the inshore resident population and (3) the populations in adjacent deepwater inlets. We provide evidence that supports the delineation of the resident and migratory stocks; and evidence of two other genetically differentiated resident groups. These results were supported by differences in biological parameters and parasite infection levels. Of note is the first record of the occurrence of the parasite Kudoa paniformis in the resident population.