Stock Differences in Growth, Smolting, and Early Male Maturation in Hatchery Spring Chinook Salmon: a Common‐Garden Experiment

Abstract

Hatchery spring Chinook Salmon Oncorhynchus tshawytscha from Parkdale Hatchery on the Hood River, Oregon, and Carson National Fish Hatchery (CNFH) on the Wind River, Washington, were reared under a common‐garden experimental regime at CNFH over three consecutive brood years (2008–2010) to assess the effects of stock on smoltification and early male maturation. Rearing groups were monitored for size, percent solid (a surrogate for whole‐body lipid), gill Na+,K+‐ATPase activity, and rate of precocious maturation in males (i.e., age‐2 minijack rate). Despite rearing of the stocks under identical conditions, the out‐of‐basin Hood River stock was significantly smaller throughout the study and at release as smolts, had lower whole‐body lipid at release, and had lower gill Na+,K+‐ATPase activity at release than the Carson stock; furthermore, the Hood River stock exhibited much higher mean minijack rates than the Carson stock (45% versus 23% of males). Using logistic regression, we demonstrated that the threshold size for initiation of early male maturation was significantly lower for the Hood River stock than for the Carson stock, suggesting a genetic basis for this life history difference. The present study highlights the importance of understanding how specific genotypes may respond differently to the unique environmental conditions in a given hatchery environment. These differences may in turn influence physiological and life history pathways that affect smolt‐to‐adult return rates and the demography of returning adults.

The Impact of Different Hatchery Rearing Environments on Smolt‐to‐Adult Survival of Spring Chinook Salmon

“…Conversely, fewer smolts could be released to achieve a similar adult return. Our findings provide insights into linkages between environmental factors that induce physiological variation and how this physiological variation may then affect smolting, early male maturation, and ultimately adult return rates for Chinook Salmon (Spangenberg et al 2014(Spangenberg et al , 2015. Finally, these findings have both conservation and economic implications for the salmon propagation community of the Columbia River basin and the Pacific Northwest.…”

Plasma 11‐Ketotestosterone in Individual Age‐1 Spring Chinook Salmon Males Accurately Predicts Age‐2 Maturation Status

“…; Spangenberg et al. , ). Thus, it appears that both genetic background and the rearing environment influence precocious maturation (Thorpe and Morgan ; Saunders ; Thorpe et al.…”

“…Therefore, production of large numbers of non‐sea‐going, precociously maturing males among hatchery‐reared age‐1+ smolts (approximately 18 months postfertilization) undermines the objective of hatchery programs to produce increased numbers of ocean‐returning adults for harvest augmentation, supplementation, and conservation of wild salmonid populations (Beckman and Larsen ; Spangenberg et al. ).…”

“…However, while observations of survival after maturation in precocious parr have been documented in spring Chinook Salmon (Rich 1920;Gebhards 1960;Bernier et al 1993), it is presumed that minijacks die after the spawning season in the natural environment (Gebhards 1960). Therefore, production of large numbers of non-sea-going, precociously maturing males among hatchery-reared age-1+ smolts (approximately 18 months postfertilization) undermines the objective of hatchery programs to produce increased numbers of ocean-returning adults for harvest augmentation, supplementation, and conservation of wild salmonid populations (Beckman and Larsen 2005;Spangenberg et al 2015).…”

“…Conservation hatchery programs for spring Chinook Salmon, which incorporate natural-origin broodstock and aim to produce fish with genetic characteristics similar to those of the native stock, have the potential benefits of reducing the short-term risk of extinction, speeding recovery, reseeding vacant habitat, and increasing harvest opportunity (Fast et al 2015). However, these integrated programs also produce minijacks at rates higher than segregated hatchery programs that only use hatchery-origin adults for broodstock (Harstad et al 2014;Spangenberg et al 2014Spangenberg et al , 2015. Thus, it appears that both genetic background and the rearing environment influence precocious maturation (Thorpe and Morgan 1980;Saunders 1986;Thorpe et al 1990;Rowe et al 1991;Larsen et al 2006;Mangel and Satterthwaite 2008).…”