Abstract

AbstractConservation hatchery strategies for anadromous salmonids are designed to boost depressed wild populations while conserving genetic resources. Captive rearing is an approach in which eggs or juveniles are collected from wild fish, taken into a hatchery and reared to maturation, and then released to spawn. In this study, we quantified spawn timing and redd production for captive‐reared and wild Chinook Salmon Oncorhynchus tshawytscha and measured survival of eggs to the eyed stage of development (egg viability) and from egg to fry. The study objective was to determine whether there was a difference in egg viability and egg‐to‐fry survival between captive‐reared and wild Chinook Salmon that spawned in the wild. During 2007–2009, 90 redds were sampled in the East Fork Salmon River, Idaho; 45 of captive‐origin salmon and 45 of wild origin. Egg viability was significantly lower for captive‐reared fish (75.0%) than for their wild counterparts (95.6%). The overall mean egg‐to‐fry survival for captive‐reared fish was quite high (80.4%), and although it was significantly lower than that for wild fish (84.0%), biologically this survival difference was not large. While others have estimated the egg‐to‐fry survival of production hatchery Chinook Salmon in the wild, it had not previously been estimated for captive‐reared fish released to spawn. Through the use of novel techniques such as hydraulic pumping and egg capsules, we were able to successfully estimate egg viability and egg‐to‐fry survival of captive‐reared and wild Chinook Salmon spawning in the wild. Although egg viability and egg‐to‐fry survival of captive‐reared fish was lower than for their wild counterparts, both survival rates may be sufficient to provide a demographic benefit to the receiving wild population.

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