Correlation between boldness and body mass in natural populations of the poeciliid Brachyrhaphis episcopi

The boldness of individual Brachyrhaphis episcopi , collected from regions of high and low predation, was investigated using two independent assays: (1) the time to emerge from cover and (2) the propensity to leave shoal mates and investigate a novel object. A strong correlation between the two assays was revealed such that fish that emerged from shelter sooner were also more likely to approach a novel object. This is indicative of a boldness personality axis acting across both behavioural contexts. Fish from high‐predation areas were bolder than those from low‐predation areas and males were bolder than females. A significant correlation between body mass, standard length ( L S ) and boldness score was also found. In general, bold fish had a greater body mass at a given L S than shy fish. These results suggest that personality traits are strongly influenced by population‐specific ecological variables and may have fitness consequences in wild populations.