CONICET | Buscador de Institutos y Recursos Humanos

The silverside (pejerrey) is a large atherinid fish commonly found in lakes of the Argentinean Pampa, which are mostly eutrophic and hydrologically unstable. This commercial species has been introduced into many countries for aquaculture and sport fishing. We aimed to evaluate the vulnerability of pejerrey populations to climate change, in the most productive pampean lake (Chasicó) and to assess others pampean water bodies. After several drought and flood events, Chasicó presents a salinity optimum (20 ppt) for the early development stages of this species. Cyanophytes that regularly cause fish mortalities were identified as Nodularia sp. and Oscillatoria sp., which are favoured by the high phosphorus concentrations (3.63 µM) and low N/P ratio (1.82) detected. In the simple trophic web of this lake, the copepod Boeckella poopoensis, particularly rich in polyunsaturated fatty acids and proteins, is the main prey of pejerrey. Cyanobacteria are poor in food quality and could decouple this low-diversity food web. Global warming is likely to amplify the intensity of droughts or inundations. Floods could prevent toxic blooms by shifting nutrient ratios but can prejudice silverside development due to its suboptimal growth at low salinities. Droughts will increase lake salinity but also its temperature and nutrient concentration. Since cyanophytes tolerate higher salinities and temperature better than other algae, toxic blooms could increase. Further, as silverside has temperature-induced reproductive dysfunctions such as thermolabile sex determination and heat-induced reduced fertility, higher temperatures can severely distort its population structure and could cause local extinction or drastic reduction of silverside stock.