Winter‐Rearing Temperature Affects Growth Profiles, Age of Maturation, and Smolt‐to‐Adult Returns for Yearling Summer Chinook Salmon in the Upper Columbia River Basin

Abstract

We assessed the effects of rearing conditions in four hatchery programs from the upper Columbia River basin on the survival and demographics of yearling summer Chinook Salmon Oncorhynchus tshawytscha over four release years. Juveniles from each hatchery program were initially reared at Eastbank Hatchery near Wenatchee, Washington, (which uses groundwater for fish rearing) and experienced similar rearing temperatures until their first autumn in culture. Fish that were to be used for two of the programs were subsequently transferred to surface water acclimation sites, where they were reared until release the following spring (surface water winter rearing). Fish to be used for the other two programs were overwintered at the Eastbank Hatchery and then transferred to their acclimation and release sites 1 to 2 months before spring release (groundwater winter rearing). Fish from the two rearing strategies experienced contrasting temperature profiles, which in turn affected winter growth, age at maturation, and smolt-to-adult survival (SAS). Overall, the two release groups that were overwintered in colder surface water experienced reduced winter growth, reduced minijack rate, and smaller size at release, but achieved a two-to threefold higher SAS than did the two release groups overwintered in warmer groundwater at Eastbank Hatchery. In addition, based on migration data compiled from fish tagged with PIT tags, smaller juveniles tended to mature at older age-classes than did larger smolts. We concluded that rearing yearling hatchery summer Chinook Salmon under more natural thermal regimes (surface water) may result in the return of larger, older adults that have a higher survival rate than would fish reared under constant or less natural thermal regimes (ground water). These results highlight the importance of the hatchery-rearing environment in shaping the survival and life history of summer Chinook Salmon juveniles released into the Columbia River basin.

Heterogeneous genetic basis of age at maturity in salmonid fishes

“…As a result, individual-level life-history data and tissue samples for genetic analyses are available for multiple populations in each of these species, making them a promising target for genotype-phenotype association studies. Chinook Salmon and Steelhead Trout exhibit the greatest variation in age at maturity (typically two to six years), Sockeye Salmon commonly mature at three to five years of age, and Coho Salmon between two and four years (Quinn, 2005), although populations can exhibit different age structures due to genetic (McKinney et al, 2019) and environmental factors such as local rearing and growing conditions (Hankin et al, 1993; Harstad, Larsen, & Beckman, 2014; Harstad et al, 2018; Taylor, 1990). Pacific salmon therefore provide an excellent opportunity to further assess the influence of six6 and vgll3 on age at maturity and improve our understanding of the extent to which genetic architectures are shared across species.…”

Influence of environmental and biological factors on the overwinter growth rate of Atlantic salmon Salmo salar parr in a UK chalk stream

“…This is potentially important, given that climate projections for southern England suggest river temperatures will increase in future winters (Watts et al, 2015). Given the positive effect of temperature on overwinter growth, these elevated temperatures are likely to result in faster winter growth rates (French, Vondracek, Ferrington, Finlay, & Dieterman, 2017; Harstad et al, 2018). Whether faster growth would result in smolts leaving the river at a larger size is, however, uncertain given that smolt migrations are anticipated to commence earlier in the season as warming rates increase (Kennedy & Crozier, 2010; Otero et al, 2014).…”

A Fish Out of Basin: Increased Stress Physiology and Reduced Performance of Salmon River Hatchery Chinook Salmon

“…The interaction between rearing conditions and juvenile‐to‐adult survival should be considered when designing, constructing, and implementing new hatchery programs (HSRG 2009). For example, significantly different smolt‐to‐adult return rates and adult age structure were reported for groups of the same genetic stock of Chinook Salmon Oncorhynchus tshawytscha that were reared at different hatchery facilities and released at the same location (Spangenberg et al 2014; Beckman et al 2017) or reared at the same facility and released at different locations (Harstad et al 2018). In both of these cases, differences between rearing and release conditions may have contributed to stocking success.…”