Parental investment and fecundity, but not brain size, are associated with establishment success in introduced fishes

1 Classical theory predicts that colonizing ability should increase with fecundity. Additionally, it has recently been shown that successful establishment of birds was correlated with relative brain size, which was suggested as possibly universal among vertebrates. 2 I conducted a comparative study of establishment success in global fish introductions, controlling for regional geographic differences, to test these hypothesized correlates. 3 In 133 introductions of 17 fish species, establishment success was negatively associated with fecundity while there was no evidence for an effect of relative brain size. In analysis of partially overlapping data, there was no evidence of a correlation between relative brain size and establishment rate across 39 species. 4 One explanation for the negative association with fecundity is that parental investment might be more important to establishment than fecundity. In 126 introductions of 14 species, reproductive behaviours associated with parental investment were significantly associated with establishment success. These results suggest that the correlation between brain size and establishment success is not universal.