E-Mail IMAGE: Mixed-stock Pacific salmon fisheries can benefit from fish biodiversity while also conserving it, if productive stocks can be selectively targeted and weak stocks avoided. view more Credit: Credit: Peter Westley. A new study, by researchers from Simon Fraser University and the Department of Fisheries and Oceans, reveals the trade-offs of fish biodiversity--its costs and benefits to mixed-stock fisheries--and points to a potential way to harness the benefits while avoiding costs to fishery performance. Many Pacific salmon fisheries catch fish that come from multiple stocks (management units), often representing locally-adapted populations, in so-called mixed-stock fisheries. Fish are intercepted in the ocean as they migrate along the coast, returning to different rivers to spawn.