The Effects of Variation in Rearing Conditions on Growth, Smolt Development, and Minijack Rate in Yearling Chinook Salmon: a Hatchery Scale Experiment

Abstract

In this investigation a single genetic stock of Hood River, Oregon, Chinook Salmon Oncorhynchus tshawytscha was reared at three different hatchery facilities over three brood years (2008–2010) and monitored for size, growth rate, gill Na+,K+‐ATPase activity, condition factor, whole body energetics, and precocious male maturation (age‐2 minijack rate). This experimental design provided a unique opportunity to isolate environmental from genetic effects on salmonid life history. Differences in the seasonal thermal regimes and associated growth profiles among the three facilities resulted in modest differences in smolt development but significant variation in size at release (range = 18 g body weight, 118 mm FL to 31 g body weight, 142 mm FL) and minijack rates (range = 4.8–57.1%) among groups. Previous studies have found a positive relationship between body size at release and minijack rates. However, in this investigation the release group with the largest mean body size consistently had the lowest minijack rates. This unique result may be due to the more natural thermal regime and feeding profile experienced by fish at this facility compared with that of the other two facilities and highlights the importance and potential benefits of adhering to a more “wildlike” growth profile in hatchery supplementation programs. Received February 24, 2014; accepted May 29, 2014

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.…”

“…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).…”

“…The physiological mechanisms involved in these decisions are not yet clear (Mangel and Satterthwaite 2008;Taranger et al 2010;Good and Davidson 2016). However, it has been demonstrated that the minijack rate increases with increased feeding and energy reserves in hatchery-reared Chinook Salmon juveniles (Larsen et al 2006;Spangenberg et al 2014).…”

Comparing Life History Characteristics of Lake Michigan's Naturalized and Stocked Chinook Salmon

“…If hatchery fish become naturalized (i.e., become established in new environments where they did not previously occur and then naturally recruit), divergence can occur between these populations and may be exacerbated if traits are heritable and either (1) naturalized populations are reproductively isolated from hatchery populations or (2) hatchery practices invoke differing selection factors than those experienced by naturalized fish. For example, hatchery practices can lead to an overproduction of precocious males in a population (micro-or minijacks) that have low reproductive success relative to wild counterparts ) and provide little harvest value to the fishery (Spangenberg et al 2014). An abundance of precocious males may have the added effect of skewing sex ratios among populations that rely on stocking for population enhancements (Larsen et al 2013).…”

The Effects of a Transition Diet on the Smoltification of Chinook Salmon

“…At hatcheries, multiple altered rearing practices have been tested to try to increase salmon survival during movement into seawater. In particular, transition diets specially formulated with supplemental dietary salt have been developed and marketed as promoting osmoregulatory development and smoltification in juvenile salmon prior to transfer to saltwater net pens or release from hatcheries (Spangenberg et al 2014). The functional basis for increasing the dietary salt content in transition diets is rooted in multiple studies of the effects of dietary salt on juvenile salmonid osmoregulatory performance and survival in salt water.…”