Community structure of fish larvae in different biotopes of a neotropical river

Spatial heterogeneity is one of the major sources of compositional dissimilarity among fish in different biotopes. The availability and distribution of refuge, food, and habitats for breeding are determinants of the presence of fish species with different life histories, and understanding how this composition is organized along an environmental gradient is important for the protection of fish spawning sites and preservation of conditions that favor the dispersion and growth of their larvae. Thus, this study aimed to evaluate how the ichthyoplankton community is structured in different biotopes (river, lake, and transitional) of a fluvial system and to determine the factors involved in the structuring process. We conducted sampling in the lower Ivinhema River, upper Paraná River floodplain, Brazil, during two consecutive reproductive periods between 2010 and 2012. Larvae of long-distance migratory species were more related to the river biotope, while the non-migratory or short-distance migrators were more associated with transitional and lake biotopes. Therefore, our results indicate that the hydrodynamic conditions of the river, especially the flow velocity, as well as the parental reproductive guild, influence the distribution patterns of the ichthyoplankton community.