In passively operated fishing gear, boldness-related behaviors should fundamentallyaffect the vulnerability of individual fish and thus be under fisheries selection. To testthis hypothesis, we used juvenile common-garden reared carp (Cyprinus carpio) withina narrow size range to investigate the mechanistic basis of behavioral selection causedby angling. We focused on one key personality trait (i.e., boldness), measured in groupswithin ponds, two morphological traits (body shape and head shape), and one lifehistorytrait (juvenile growth capacity) and studied mean standardized selection gradientscaused by angling. Carp behavior was highly repeatable within ponds. In the shortterm, over seven days of fishing, total length, not boldness, was the main predictor ofangling vulnerability. However, after 20 days of fishing, boldness turned out to be themain trait under selection, followed by juvenile growth rate, while morphological traitswere only weakly related to angling vulnerability. In addition, we found juvenile growthrate to be moderately correlated with boldness. Hence, direct selection on boldnesswill also induce indirect selection on juvenile growth and vice versa, but given that thetwo traits are not perfectly correlated, independent evolution of both traits is also possible.Our study is among the first to mechanistically reveal that energy-acquisitionrelatedbehaviors, and not growth rate per se, are key factors determining theprobability of capture, and hence, behavioral traits appear to be the prime targets ofangling selection. We predict an evolutionary response toward increased shyness inintensively angling-exploited fish stocks, possibly causing the emergence of a timiditysyndrome.
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