Behaviour 2019
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Size-selective mortality affects collective risk-taking under predation threat in zebrafish, Danio rerio
Tamal Roy1, Robert Arlinghaus1,2. 1Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) Berlin and Humboldt University of Berlin, Berlin, , Germany; 2Humboldt University of Berlin, Berlin, , Germany

Size-selective mortality is common in fish-populations and can operate either in positive (e.g. fisheries) or negative (e.g. gape-limited predation) size-selective fashion thereby fostering evolutionary changes in behaviour. Theory suggests that size-selection alone favours boldness, but little experimental evidence exists about whether and to what extent size-selection can trigger its evolution. Here we investigated impacts of size-selective mortality on boldness across ontogeny using three experimental lines of zebrafish generated through positive (large-harvested), negative (small-harvested) and random (control line) size-selective mortality for five generations. We measured risk-taking in zebrafish under simulated aerial predation threat and in presence of a cichlid by estimating time spent at water-surface for feeding. Under aerial threat, fish among selection lines did not differ in boldness in the larval stages. Post this, small-harvested line fish were bolder than controls, while large-harvested and control line fish did not differ. In adults in presence of cichlid, large-harvested line fish were bolder than controls when they perceived both visual and olfactory cues.