Body size and population dynamics of annual fishes from temporary wetlands in Southern Brazil

Abstract

Annual fishes live exclusively in temporary wetlands where several species coexist. Understanding how annual fishes cohabit in small and isolated pools is still a challenge. In this study, we aimed to examine the prediction that annual fish assemblages in temporary pools in Southern Brazil are structured by temporal differences in body size, specific growth rate and density. Two–three fish species coexisted in each pool. The most abundant and frequent species were Cynopoecilus melanotaenia and Austrolebias nigrofasciatus, while A. wolterstorffi was less abundant and rare. The species differed significantly in body size throughout the flooding phase and showed similar growth patterns, with higher specific growth rates in the first months of flooding and a reduction in growth rate thereafter. The monthly average densities of A. nigrofasciatus and C. melanotaenia did not differ over time, but they were higher than values observed for A. wolterstorffi. Our results provide evidence for hatching synchrony, similar specific growth rates and densities among the most abundant species and differences in body sizes among all species that are more evident after adulthood, suggesting that differences in body size mediate the coexistence of annual fishes in temporary pools.