Patterns of spatial and temporal distribution of fish eggs and larvae in the Pardo and Anhanduí rivers, Upper Paraná river basin, Brazil

Abstract

In this study we assessed the spatial and temporal distribution of ichthyoplankton and their reproductive strategies into the Pardo and Anhanduí rivers, located on the right bank of the Paraná river, MS. Samples were obtained from October/2009 to March/2010 using conical-cylindrical plankton net for surface samples at nightfall. In general, the family  Anostomidae was the most abundant in this study. We also registered eight migratory species: Prochilodus lineatus; Salminus brasiliensis; Brycon orbignyanus; Rhaphiodon vulpinus; Hemisorubim platyrhynchos/Pseudoplastytoma corruscans; Pimelodus maculatus; Sorubim lima and Zungaro zungaro. However, the sedentary species without parental care were more representative. Considering larval stages of development, significant differences were found for the stage of post-flexion at the mouths of rivers. A spatial pattern of eggs and larvae was registered: eggs were more abundant in the upstream stretches of the rivers and larvae in the downstream stretches. Higher abundances of eggs were found from october to january, and larvae in november, december and january. We conclude that Pardo as Anhanduí are suitable areas for spawning and early development of several fish species. This was clearly observed for the marginal lagoon into the Pardo river, where we registered higher occurrences of larvae in relation to the other sampling stations performed for both rivers.