Environmental predictors for annual fish assemblages in subtropical grasslands of South America: the role of landscape and habitat characteristics.

Annual fishes (AF) are ecologically unique assemblage with major conservation concern. Several AF species are found in temporary waters of South American subtropical grasslands, an ecoregion largely neglected by conservation policies. We applied a broad-scale approach to understand distribution pattern of the AF and tested the effects of environmental predictors on occurrence, abundance and assemblage structure of this diverse Neotropical group of threatened endemic aquatic fauna. We recorded 23 AF species. AF assemblage was strongly spatially structured and many individual species formed discrete units. AF presence was negatively associated with altitude at the landscape scale, and negatively associated with maximum pool depth and presence of predatory fish at the local scale. We found negative association between AF abundance and water depth. Assemblage composition was spatially structured, differed among hydrographic regions and was influenced by altitude, temperature and monthly precipitation. AF inhabits highly vulnerable habitats currently located in livestock and agricultural landscapes. Habitat maintenance through wildlife-friendly practices should be considered as an alternative to promote AF conservation. [ABSTRACT FROM AUTHOR]