High plasticity in short- and medium-scale movements in two catfish species from the Paraná Basin

Abstract

Oxydoras kneri and Hemisorubim platyrhynchos are catfish species of high ecological and commercial relevance from the Paraná River (La Plata Basin, South America) whose life history remains unknown. The aim of this study was to reveal the nursery areas and describe the habitat use throughout the ontogeny of both catfish species from the Paraná River using the otolith 87Sr/86Sr ratio. Otolith core-to-edge 87Sr/86Sr analyses were measured using a LA-MC-ICPMS system. A Quadratic Discriminant Analysis (Wilks? Lambda = 0.029, p < 0.0001) based on the water 87Sr/86Sr baseline of the La Plata Basin was run to infer the natal origin using the core 87Sr/86Sr ratio as an independent variable. Oxydoras kneri was classified as originating from Paraguay (35.7%), middle Paraná (57.1%), and upper Paraná (7.1%) rivers, while H. platyrhynchos was classified as originating from the middle (56.3%) and upper (43.7%) Paraná River. Otolith 87Sr/86Sr time series suggested a high complexity in the stock structure of both species from upper Paraná River, with a significant contribution of specimens originating in other areas. Both species showed isotopic variations in their otoliths compatible with short- and medium-scale movements between different reaches of the Paraná and Paraguay rivers that could exceed 200 km.