The amphibian macrophyte Polygonum punctatum as a temporary habitat and feeding ground for fish

Abstract

Plants that colonize wet habitats may become temporarily submerged forming a new habitat for fish in the flood period. In this study, the amphibian macrophyte Polygonum punctatum was evaluated as a temporary habitat and feeding ground for fish (≤ 108 mm) during the flood period in a river–floodplain ecosystem. The fish were sampled in January and February of 2015 in a lake of the Upper Parana River floodplain, inside patches dominated by P. punctatum (flood-formed, temporary habitat) and Eichhornia azurea (permanent aquatic habitat, used as control). The abiotic data did not differ between the two plants, unlike their biomass, which was higher for E. azurea. Fish abundance did not differ between macrophytes but the composition and richness did, with more species registered in E. azurea. The foraging efficiency of fish was significantly lower in individuals using the amphibian macrophyte for most species. Differences in the diet composition were verified for half of the species, but the main items consumed were the same in both macrophytes, changing only the proportion. The niche breadth was similar in the patches of both macrophytes. The results suggest that during flood periods, the new habitat provided by the macrophyte P. punctatum was colonized by small fish that probably used this new habitat as a refuge and feeding ground. However, the lower foraging efficiency in this macrophyte suggests that it does not provide an amount of food resources comparable to the permanent habitat represented by E. azurea.