Assessment of mixed-stock fisheries and hatchery broodstocks for coho salmon in British Columbia, Canada via parentage-based tagging and genetic stock identification

Abstract

Genetic stock identification (GSI) and parentage-based tagging (PBT) are being increasingly applied to salmon fisheries and hatchery broodstock management and assessment in Canada. GSI and PBT were applied to assessment of 2019 coho salmon fisheries and hatchery broodstocks in British Columbia (BC), Canada, with 8208 individuals successfully genotyped in fishery samples and 2237 PBT identifications made (27.3% individual identification rate). The observed number of fishery PBT identifications per population corresponded closely with the expected number based upon genetic tagging rate in the populations. Coded-wire tags (CWTs) did not provide an accurate representation of the catch in the northern British Columbia troll fishery or the northwest Vancouver Island inshore recreational fishery, owing to the fact that major components of this fishery were not marked with CWTs. A single population chosen as an indicator in a Conservation Unit (CU) did not display a distribution of captures among fishery areas that was representative of other populations in the CU. There were 6544 individuals genotyped in 25 hatchery broodstocks from which 4019 PBT identifications were made. Population-specific contributions to mixed-stock fisheries and exploitation rates were estimated with CWTs and GSI-PBT technologies for eight hatchery populations. There was generally reasonably close agreement of estimated population-specific exploitation rates between CWT and genetic methods for hatchery populations. We conclude that a genetic approach can improve upon the results available from the current CWT program for assessment and management of coho salmon fisheries and hatchery broodstocks in BC, and provide information critical to aid in implementation of Canada’s Policy for Conservation of Wild Pacific Salmon.