Abstract
This study found empirical evidence supporting the “growth–survival” paradigm in the marine phase of Arctic char (Salvelinus alpinus) and brown trout (Salmo trutta). The paradigm postulates that larger or faster-growing individuals are more likely to survive than smaller or slower-growing conspecifics. The study employed long-term (25 year) capture data from a trap in the River Halselva in Norway during annual migration between marine and freshwater environments. Similar results were found for both species. Growth during the sea sojourn and return rates were positively correlated, linking increased survival with growth. Specific growth rate, survival, and duration of the sea sojourn of first-time migrants were correlated, suggesting that common environmental conditions at sea influence annual fish productivity. Freshwater and sea temperatures affected migration timing, whereas annual variation in marine growth and survival did not correlate with temperatures. This suggests that other factors such as variation in energy intake were the main source of annual growth variations. Moreover, the marine growth rate of the two species may signal annual overall fjord ecosystem production, especially related to their main prey.
Highlights
The “growth–survival” paradigm is influential in the study of marine fish recruitment dynamics (Ottersen and Loeng 2000; Houde 2008; Pepin et al 2015); it postulates that size, growth rate, or both factors during early life are positively correlated to survival (Anderson 1988)
20 km of the watercourse is accessible to anadromous salmonids (Arctic char, brown trout, and Atlantic salmon), including a 1.2 km2 lake located 2.1 km inland and 30 m above sea level (Lake Storvatn) (Fig. 1)
No significant temporal trends were detected during the 25 year period regarding duration of the first sea sojourn, standardized mass-specific growth rate ⍀, seasonal mass increment, or return rate for any of the two species
Summary
The “growth–survival” paradigm is influential in the study of marine fish recruitment dynamics (Ottersen and Loeng 2000; Houde 2008; Pepin et al 2015); it postulates that size, growth rate, or both factors during early life are positively correlated to survival (Anderson 1988). Some results from studies of anadromous salmonids suggest that a positive relationship between growth and survival may exist during the marine life stage (Friedland et al 2009). In long-term tagging studies with two Atlantic salmon (Salmo salar) populations in the North Sea, positive correlations were found between growth of post-smolts (i.e., during the first summer at sea) and sea temperature conditions, and high growth led to higher return rates (Friedland et al 2000). Retrospective analyses of circuli spacing from long-term scale-sample data established relationships between post-smolt growth and sea surface temperatures in two European Atlantic salmon populations, again linking growth to abundance and survival (Peyronnet et al 2007; McCarthy et al.2008)
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