Timing of spawning and predicted fry emergence by naturalized Chinook salmon (Oncorhynchus tshawytscha) in a Lake Huron tributary

Evolutionary Applications

2017

Offspring traits are greatly influenced by maternal effects, and these maternal effects may provide an important pathway through which populations can adapt to changing thermal environments. We investigated the effect of egg size on the among‐ and within‐population variation in early life history traits among introduced Great Lakes Chinook salmon (Oncorhynchus tshawytscha) populations under varying thermal conditions. We reared Chinook salmon from three populations in a common‐garden hatchery study at 6.5, 9.4, and 15.2°C and measured a variety of fitness‐related traits during development. We found that most of the among‐population variation in early life history traits was explained by egg size. However, the contribution of egg size to the among‐population variation decreased with an increase in temperature suggesting that other effects, such as genetic, contribute at high temperature. Within populations, egg size explained much of the dam variance and maternal effect for traits in every temperature, whereas egg size generally had little to no influence on the sire variance and heritability. Overall, our results demonstrate the significant contribution egg size makes to shaping early life history phenotypes among and within populations, and suggest that egg size is an important pathway through which offspring phenotypes can evolve on contemporary timescales.

Section: Methodsmentioning

confidence: 99%

Egg size and the adaptive capacity of early life history traits in Chinook salmon (Oncorhynchus tshawytscha)

Thorn

Evolutionary Applications

2017

“…Our results of increasing prespawning movements with arrival date are consistent with density-dependent movement. Moreover, findings of high rates of egg retention and nest superimposition (Gerson et al 2016) provide evidence of active density-dependent mechanisms among females (Kinnison et al 1998;Quinn et al 2007;Schroder et al 2008). In the Sydenham River, the approximately 3.5 km of suitable habitat may simply be too limited given the numbers of returning females (484 in 2010; 536 in 2011), with the best habitat occurring close to the stocking site (sections B and C), for spawning distributions to differ between rearing origins.…”

Section: Spawning Distributionsmentioning

confidence: 99%

“…Shoreline surveys were not conducted in other areas of the river because the shoreline was not readily accessible. Similar to Gerson et al (2016), 3-min behavioral observations were performed to identify tagged individuals and determine reproductive status (i.e., settled on nest[s] or not). Females were considered to have settled on a nest if nest defense (aggression toward males and other females), digging, or spawning behaviors (egg deposition) were observed.…”

Section: Marklevitz and Morbeymentioning

confidence: 99%

Habitat Use and Arrival Timing of Hatchery and Naturalized Chinook Salmon Spawning in a Great Lakes Tributary

Marklevitz

2017

Trans Am Fish Soc

Large‐scale stocking programs have been used to introduce and maintain Chinook Salmon Oncorhynchus tshawytscha fisheries in the Laurentian Great Lakes since the late 1960s, with discoveries of naturalized populations in tributaries soon after the initial introduction. Characterizing ecological differences between hatchery and naturalized Chinook Salmon is becoming increasingly important for sustainable management of this species. We hypothesized that nonheritable traits (i.e., homing) and artificial selection might result in different habitat use and arrival timing between rearing origins occupying the same river, with the potential for reproductive isolation and divergence of naturalized and hatchery strains. In 2010 and 2011, using visual observations and PIT tags, we tracked individual hatchery and naturalized Chinook Salmon that spawned in the Sydenham River (Owen Sound, Ontario), one of the first tributaries in Lake Huron to be colonized by hatchery strays and establish a naturalized population. We estimated that 52–58% of the 3,200–3,300 fish returning to spawn in 3.5 km of accessible spawning habitat were hatchery fish. In females, the extent of prespawning movement increased with arrival date, decreased with fish length, and was lower for hatchery fish. Hatchery females also displayed a higher probability of direct homing to the stocking site than naturalized females. Prespawning movements by males were extensive but did not depend on rearing origin, arrival timing, or body size. We found no evidence of reproductive isolation, however. Spatial distributions of spawning locations were independent of rearing origin for both sexes, and arrival timing in the river was similar between rearing origins for both sexes. The lack of reproductive isolation is likely attributable to the small area of suitable habitat in this river. Our study represents the first comprehensive comparison of spawning habitat use and timing by hatchery and naturalized Chinook Salmon in the Great Lakes. Received October 26, 2016; accepted February 22, 2017 Published online April 24, 2017

“…We estimated fecundity for each simulated female from both populations by using a linear model that was fit to the Sydenham River female length and fecundity data collected by Gerson et al. () in 2010 and 2011 (fecundity = [13.906 × female length] − 4,802.239). Random deviations were added to the fecundity predictions by drawing from a normal distribution with a mean of zero and an SD of 1,267.4. Use population‐specific egg mass–in situ survival relationships that were fit by using logistic regression to predict the proportion of eggs that will hatch for each simulated female (Credit River: log[survival/1 − survival] = [0.3938 × egg mass] − [1.5528 × egg mass 2 ] − 1.8162; Sydenham River: log[survival/1 − survival] = [0.6703 × egg mass] − 0.4295).…”

Section: Methodsmentioning

confidence: 99%

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

Thorn

2019

Trans Am Fish Soc

Early‐life mortality in salmon is influenced by both extrinsic (i.e., environmental) and intrinsic (i.e., parental) factors; however, the intrinsic factors have rarely been studied in the wild and relatively little is known about how egg mass and parental effects mediate in situ survival. Thus, we addressed four research objectives related to intrinsic factors and the early‐life survival of Chinook Salmon Oncorhynchus tshawytscha: (1) assess the effect of egg mass and parental effects on in situ hatching success, (2) assess the effect of redd gravel composition and its interaction with egg mass on in situ hatching success, (3) determine whether in situ egg mass–survival relationships have population‐level consequences, and (4) determine whether results from hatchery studies translate to the wild. Embryos from three Chinook Salmon populations located in the Laurentian Great Lakes were reared from fertilization to 15 d posthatch, both in the hatchery and in the wild. We found that egg mass influenced in situ hatching success in the Credit (concave down) and Sydenham rivers (positive‐linear), whereas there was no relationship between the two variables in the Pine River. Maternal identity explained a significant amount of the variation in hatching success for the Pine (20%) and Sydenham (12%) rivers. Within populations, no interaction was found between egg mass and gravel composition; however, hatching success was negatively related to the sand content of a redd when the data were pooled among the populations. Importantly, egg mass and quantitative genetic parameter estimates were different between samples from the hatchery and those from the wild, indicating that hatchery‐based observations cannot be transferred to the wild. Finally, we used both the in situ survival data and previously published data in a simulation analysis, which showed that both linear and nonlinear egg mass–survival relationships can greatly influence the number of alevins produced by a population, depending on where the population egg mass distribution falls along an egg mass selection gradient.