Variability in the trophic position of larval fishes in theupper Paraná floodplain based on δ15N

Abstract

The upper Paraná River floodplain is composed of several marginal lagoons, making it a natural breeding ground for many fish species at developmental stages. The aim of this study is to estimate the trophic positions of these fishes based on feed intake (measured via diet) and nitrogen assimilation (measured via δ 15 N). The monthly samplings were concentrated during the spawning season in the Ivinheima River, which is located in the upper Paraná River floodplain. The specimens were grouped into preflexion, flexion and postflexion stages. Trophic positions were estimated based on the isotope value of nitrogen and on diet. During the developmental stages of P. squamosissimus, there were significant differences in the isotope values of δ 15 N; for H. edentatus, however, no significant differences were found. During the developmental stages, both species were classified as either at or above the third trophic level. Once this information is obtained for other species and components of the ecosystem, it will not only provide a more precise view of the energy allocation and flow in the ecosystem, but will also make possible for management measures to promote sustainability in this environment.

Diel vertical migration and spatial overlap between fish larvae and zooplankton in two tropical lakes, Brazil

“…Studies performed in the region of the Upper Paraná River floodplain related to the vertical distribution of zooplankton community are limited to very few studies, such as Tomm et al (1992) and Lansac-Tôha et al (1995), whereas studies on the vertical distribution of ichthyoplankton community are lacking, and studies relating both communities are restricted to those investigating the feeding of fish larvae, including Makrakis et al (2005; and Manetta et al (2011). According to Mehner (2012), there is no recent literature available regarding the mechanisms of DVM in freshwater fish.…”