Provenance matters: thermal reaction norms for embryo survival among sockeye salmon Oncorhynchus nerka populations

Abstract

Differences in thermal tolerance during embryonic development in Fraser River sockeye salmon Oncorhynchus nerka were examined among nine populations in a controlled common‐garden incubation experiment. Forcing embryonic development at an extreme temperature (relative to current values) of 16° C, representing a future climate change scenario, significantly reduced survival compared to the more ecologically moderate temperature of 10° C (55% v. 93%). Survival at 14° C was intermediate between the other two temperatures (85%). More importantly, this survival response varied by provenance within and between temperature treatments. Thermal reaction norms showed an interacting response of genotype and environment (temperature), suggesting that populations of O. nerka may have adapted differentially to elevated temperatures during incubation and early development. Moreover, populations that historically experience warmer incubation temperatures at early development displayed a higher tolerance for warm temperatures. In contrast, thermal tolerance does not appear to transcend life stages as adult migration temperatures were not related to embryo thermal tolerance. The intra‐population variation implies potential for thermal tolerance at the species level. The differential inter‐population variation in thermal tolerance that was observed suggests, however, limited adaptive potential to thermal shifts for some populations. This infers that the intergenerational effects of increasing water temperatures may affect populations differentially, and that such thermally mediated adaptive selection may drive population, and therefore species, persistence.

Optimum and maximum temperatures of sockeye salmon (Oncorhynchus nerka) populations hatched at different temperatures

“…The ABT analysis was performed for each individual fish according to Yeager and Gordon (1989), and a mean value (Table 3) was calculated for each temperature treatment group. Migration temperatures, spawning temperatures, and migration distances that were used for the correlation analyses with CTmax were obtained from Whitney et al (2013). Spawning temperatures were calculated from the mean historical temperature of peak spawning period.…”

“…1). The eggs were fertilized and incubated at The University of British Columbia at 10, 14, and 16°C (for details see Whitney et al 2013), which yielded 27 temperature treatment groups that were maintained separately at these temperatures until hatch. Survival at hatch varied among populations and temperatures, ranging between 45% and 94.2% at 10°C, between 46.1% and 85.4% at 14°C, and between 14.2% and 55.8% at 16°C (Table 1).…”

Are there intergenerational and population-specific effects of oxidative stress in sockeye salmon (Oncorhynchus nerka)?

“…There was also significantly higher liver antioxidant capacity in Stellako River females compared to Chilko River females (z = 3.81, p b 0.01). No differences in liver antioxidant capacity was detected between Chilko River and Harrison River females (z = 0.39, p = 1.000) or Stellako River Table 1 Population-specific migration characteristics for the three study populations of Oncorhynchus nerka, including adult migration distance, elevation, effort and temperature, a description of where the rearing areas are for fry, the direction and distance fry must migrate to reach these areas from spawning grounds following emergence (Eliason et al, 2011;Sopinka et al, 2013;Whitney et al, 2013 and Harrison River females (z = 2.65, p = 0.244). Oxidative stress was highest in brain tissue of Harrison River females, which was higher than levels in Stellako (z = −4.49, p b 0.001), but not Chilko River females (z = 2.09, p = 0.3654).…”

Using watershed characteristics to inform cost-effective stream temperature monitoring

“…We define high-temperature streams as streams that are likely to exceed some biologically relevant threshold. For example, it has been suggested that temperatures [15°C can have negative impacts on spawning, incubation (Whitney et al 2013) and rearing salmonids (Stalberg et al 2009). We applied our framework using 15°C but any temperature could be used to accommodate differences in thermal thresholds among species and populations; this could also include minimum temperature thresholds.…”