Article

Upper thermal limits on the oceanic distribution of Pacific salmon (Oncorhynchus spp.) in the spring

Canadian Journal of Fisheries and Aquatic Sciences (Impact Factor: 2.32). 04/2011; 52(3):489-503. DOI: 10.1139/f95-050

ABSTRACT Pacific salmon are normally thought to be distributed throughout the Subarctic Pacific, an area where they form the dominant fish fauna. We use a series of generalized additive models to show that salmon exhibit a sharp step-function response to temperature in the oceanic eastern north Pacific in spring. The critical temperature defining the southern boundary varied by species: 10.4 °C for pink and chum salmon, 9.4 °C for coho salmon, and 8.9 °C for sockeye salmon. These thermal limits occur well to the north of the southern boundary of the Transition Zone, at widely separated geographic positions within the Subarctic Domain, and at temperatures much lower than the lethal upper limit for each species. The sharp decline in abundance with temperature, and the remarkably low temperatures at which the response occurs, suggests that thermal barriers form an effective limit to the offshore distribution of salmon in spring, and can limit the distribution of Pacific salmon to a relatively small area of the Subarctic Pacific. The strength of this response is presumably the direct result of strong evolutionary selection. Future temperature changes in the North Pacific could therefore have a direct impact on the production dynamics of Pacific salmon.

0 Bookmarks
 · 
40 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Coho salmon (Oncorhynchus kisutch) populations that spawn in the coastal rivers of Oregon, U.S.A., formerly supported robust fisheries but are now listed as a “threatened species” under the U.S. Endangered Species Act. Climate change is an increasing concern in salmon conservation, and we assess the effects of climate change on sustainability of this population group. Four distinct habitats are important to different life-history stages of coho salmon: terrestrial forests, freshwater rivers and lakes, estuaries, and the ocean. Each of these habitats is affected by multiple aspects of climate change, resulting in a complex web of pathways influencing sustainability. We summarize regional climate change studies to predict future climate patterns affecting these habitats, identify the ecological pathways by which these patterns affect coho salmon, and review coho salmon ecology to assess the likely direction and magnitude of population response. Despite substantial uncertainties in specific effects and variations in effects among populations, the preponderance of negative effects throughout the life cycle indicates a significant climate-driven risk to future sustainability of these populations. We recommend that management policies for all four habitats focus on maximizing resilience to the effects of climate change as it interacts with other natural and anthropogenic changes.
    Northwest Science 01/2013; 83(3):219-242. · 0.51 Impact Factor
  • Source
    PLoS ONE 01/2012; · 3.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We review literature concerning the impacts of climate change on the migration of marine species, with an emphasis on the adaptation of migration phenology through genetic tracking and phenotypic plasticity. We then develop an individual-based modeling framework characterizing the effects of climate change on phenology and population dynamics. In the framework, an animal's ability to match its environmental preferences, its bioclimate envelope, to the environmental conditions by adjusting its migration timing between foraging and breeding habitats determines its condition, survival, and fecundity. Climate-induced changes in the envelope produce timing mismatches that result in a population adapting its phenology through both genetic and plastic processes. Model results suggest: (1) the temporal size of the bioclimate envelope is an important determinant of a population's sensitivity to climate change and susceptibility to extinction, (2) population extinction can occur if the rate of change in the timing of the envelope exceeds the rate its phenology changes or if the variability in the envelope exceeds the population's inherent capacity for variability, (3) a population with migration timing cued by photoperiod is expected to exhibit weaker phenotypic plasticity than one cued by temperature, and (4) population extinction in response to climate change follows a threshold pattern such that population size may not be a reliable indicator of extinction threat, although variability in average individual condition across years may be an extinction threat indicator. Finally, while the model is intentionally simplistic, we discuss how it can be extended to cover more complex interactions.
    Ecological Modelling 01/2013; 264:83-97. · 2.07 Impact Factor

Full-text

View
1 Download
Available from