Diversidad de peces en el estuario externo del río Negro, Rio Negro, Argentina

Abstract

Wetlands are aquatic ecosystems that include marshes, swamps, and estuaries, the latter being considered transition areas between freshwater and marine environments. Estuaries are crucial for biodiversity as they serve as habitats for various fish species, especially during juvenile stages. They also play a fundamental role in human economic activities, such as local and artisanal fishing. However, overfishing and pollution threaten the health of these ecosystems. The Río Negro estuary, located in the Patagonian region, is an example of a wetland facing the aforementioned ecological pressures. Despite its importance, there are few studies on its ichthyofauna and socio-environmental aspects. The aim of this study was to survey the fish species of the external Río Negro estuary to provide data that promote conservation and fisheries management in the area. The methodology consisted of seasonal sampling over the course of a year at four sites in the Río Negro estuary. Each sampling was conducted during low tide and the transition to high tide. Additionally, contributions from local sport fishermen were included. A total of 2,905 fish were collected, belonging to 11 species, 10 families, and 7 orders. First-time records included Engraulis anchoita, Ramnogaster arcuata, Brevoortia aurea, and Patagonotothen sima. The silverside (Odontesthes argentinensis) and B. aurea represented 95.55% of the most captured species in the samplings, with silverside being the only species recorded in all stations. Regarding the information provided by fishermen and supplemented by the data from this study, a total of 29 species, 25 families, and 17 orders were recorded. For the first time, the Simpson Diversity Index was calculated for the Río Negro estuary, with the highest value obtained during the summer season (0.45). The Length-Weight relationship was also estimated for the most abundant species (B. aurea, O. argentinensis, and R. arcuata). Using the data collected, the Relative Condition Index (Kn) was calculated for each of the previously mentioned species at each developmental stage analyzed. Finally, the presence of juveniles at all sampling sites indicates that the populations complete their life cycle in this section of the Río Negro, confirming the importance of such ecosystems for marine biodiversity. Additionally, measures for the conservation and management of fishery resources in the estuary are necessary.