A Quantitative Evaluation of Survival to the Adult Stage and Other Characteristics of Pink Salmon (Oncorhynchus gorbuscha) Produced by a Revised Hatchery Method Which Simulates Optimal Natural Conditions

Abstract

To evaluate a hatchery method utilizing a gravel medium and filtered water during incubation, comparisons were made between naturally and artificially propagated parts of one native stock of pink salmon (Oncorhynchus gorbuscha) of the Tsolum River, B.C. Yolk utilization (growth rate) of fry was unimpeded in the hatchery environment, but hatchery fry migrated about 6 days earlier than creek fry. Hatchery survival was about six times that in the creek. The main test criterion — relative survival to the adult stage of fish from both treatments following migration from the creek — was tested by release of two similar groups of fry identified by a double finclip and recovery of marked adults upon return. Both groups survived at virtually the same rate. Numbers of actual mark recoveries were adequate to demonstrate statistically that survival of hatchery fish following release was not less than 90% of creek fry survival and that the final gain ratio of the hatchery treatment was not less than 5.44 (P <.005). Adult size, sex ratio, fecundity, and timing were not adversely affected by the hatchery treatment.