Egg Viability and Egg‐to‐Fry Survival of Captive‐Reared Chinook Salmon Released to Spawn Naturally

Abstract

Conservation 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.

The Productivity and Viability of Snake River Sockeye Salmon Hatchery Adults Released into Redfish Lake, Idaho

“…; Stark et al. ). Juvenile fitness‐related traits such as size and emergence timing have also been linked to maternal phenotype (Braun et al.…”

“…Other studies have indicated differential reproductive success between hatchery and natural conspecifics (Fleming and Gross 1993;Fleming and Petersson 2001;Williamson et al 2010;Anderson et al 2012;Ford et al 2012;Kozfkay et al 2017) and have related this difference to age at maturation, fish size and competition, timing of spawning, redd construction and location, or egg viability (Williamson et al 2010;Anderson et al 2012;Ford et al 2012;Stark et al 2018). Juvenile fitness-related traits such as size and emergence timing have also been linked to maternal phenotype (Braun et al 2013).…”

Efficacy of a Short‐Term Captive Broodstock Program Compared with Hatchery‐Origin Spring Chinook Salmon Derived from the Same Population

“…For example, Gallinat and Chang (2013) found significantly lower reproductive potential in captive brood and supplementation-reared females compared with natural-origin females of the same stock, with fecundity decreasing as time spent in the hatchery environment increased. Stark et al (2018) also found significantly lower egg viability and egg-to-fry survival from captivereared salmonids compared with natural-origin salmonids spawning in the East Fork Salmon River. Many of the biological changes that can occur as the result of captivity are unknown (Horreo et al 2017), but reducing the number of generations in captivity is expected to reduce the extent or degree of domestication selection (Frankham 2008;Horreo et al 2017).…”

“…Stark et al. (2018) also found significantly lower egg viability and egg‐to‐fry survival from captive‐reared salmonids compared with natural‐origin salmonids spawning in the East Fork Salmon River. Many of the biological changes that can occur as the result of captivity are unknown (Horreo et al.…”

Survival under the Gravel: the Effects of Egg Size and Parental Identity on the In Situ Hatching Success of Chinook Salmon

“…; Stark et al. ). Laboratory studies have shown that intrinsic factors can greatly influence early‐life survival in salmonids either independently or through an interaction with extrinsic factors (Heath et al.…”