Evaluation of population-specific behavioural impairment and mortality in salmon incidentally captured in marine commercial purse seine fisheries

While targeting abundant species, Canadian commercial seine net fisheries for Pacific Salmon inadvertently capture species of concern that are required to be released. The survival of these released salmon is a key component of assessing the impacts of seine fisheries and developing harvest limits. However, there is poor understanding of post-release mortality in general, especially in chum salmon. Additionally, the handling and release practices employed by the commercial purse seine fleet are inconsistent among individual vessels, likely influencing the probability of survival for released fish.

If handling and release practices can be identified that beget good survival, their implementation would reduce mortality of salmon released from the entire fleet. Adoption of consistent and appropriate release practices will additionally appease public concerns, increase efficiency of harvest, potentially allow additional harvest opportunities and reduce impacts on stocks of concern. Moreover, sociological human dimensions research conducted this past year has identified that commercial fishers would be more willing to modify handling practices if the rationale for doing so was supported by scientific results.

In concert with this finding, the results of this study as well as those from previous research with the commercial fleet has been, and will continue to be, presented to staff from the Canadian Fishing Company (Canfisco), relevant environmental groups, and commercial fishers through seiners associations and advisory boards. Using the 2016 Pacific salmon purse seine fishery in Canadian Statistical Area 3 as a model system, we propose to evaluate how variable handling and sorting practices influence survival and condition following release, and how these relationships change throughout the season.