Nonrepresentative fish and ocean migration assumptions confound inferences in Rechisky et al.

Close examination of the methods, assumptions, and results of Rechisky et al. (1) indicate that their results are confounded by nonrepresentative tagging, rearing, and release factors, and that critical assumptions are inconsistent with available data. Thus, the authors’ conclusions regarding hydrosystem-related delayed mortality are overreaching and unsupportable. Nonrepresentative fish with acoustic tags were 10–20 mm longer, were released 21–83 d later, and were released 55–249 rkm further downriver than their corresponding hatchery populations of inference. Length at tagging, timing of release (2), and migration distance have all been shown to influence survival rates of Chinook salmon at …