Abstract
AbstractRecruitment variability in many fish populations is postulated to be influenced by climatic and oceanographic variability. However, a mechanistic understanding of the influence of specific variables on recruitment is generally lacking. Feeding ecology is one possible mechanism that more directly links ocean conditions and recruitment. We test this mechanism using juvenile Chinook Salmon (Oncorhynchus tshawytscha) collected off the west coast of Vancouver Island, British Columbia, Canada, in 2000–2009. Stable isotopes of carbon (δ13C), an indicator of temperature or primary productivity, and nitrogen (δ15N), an indicator of trophic position, were taken from muscle tissues of genetically stock‐identified salmon. We also collated large‐scale climate indices (e.g., Pacific Decadal Oscillation, North Pacific Gyre Oscillation), local climate variables (e.g., sea surface temperature) and copepod community composition across these years. We used a Bayesian network to determine how ocean conditions influenced feeding ecology, and subsequent survival rates. We found that smolt survival of Chinook Salmon is predicted by their δ13C value, but not their δ15N. In turn, large‐scale climate variability determined the δ13C values of salmon, thus linking climate to survival through feeding ecology, likely through qualities propagated from the base of the food chain.
Highlights
Climate and ocean conditions influence the recruitment variability and early survival rates of many fish species (Aebischer et al, 1990; Platt et al, 2003; Ware and Thomson, 2005)
We modelled the interannual variability in the survival of Chinook Salmon in the Northern California Current as a function of climate variables that have previously been linked to growth or survival
Stable isotope analysis was performed on a total of 555 juvenile Chinook Salmon that were captured during the fall of 2000–2009
Summary
Climate and ocean conditions influence the recruitment variability and early survival rates of many fish species (Aebischer et al, 1990; Platt et al, 2003; Ware and Thomson, 2005). The direct mechanisms underlying the linkages between climate and fisheries are not well-understood (Baumann, 1998) and relationships between environmental variables and recruitment often break down over time (Myers, 1998). Pacific salmon (Oncorhynchus spp.) are an anadromous and semelparous species whose recruitment variability and survival have repeatedly been linked to climate. The Pacific Decadal Oscillation (PDO) (Mantua et al, 1997) and the North Pacific Gyre Oscillation (NPGO) (Kilduff et al, 2015) are large-scale climate indices that both have been correlated with interannual variability in salmon recruitment. A mechanistic understanding of the intermediate steps between climate and recruitment is often lacking (Baumann, 1998; Malick et al, 2015a)
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