Influence of the fish introduction in lakes of the arid southern Patagonia

MARÍA SOL, PORCEL; FRANCISCO, SAAD JUAN; MARINONE, M CRISTINA; IRINA IZAGUIRRE; JULIO L. LANCELOTTI

The Freshwaters and Wetlands of Patagonia Ecosystems and Socioecological Aspects

Springer

Año: 2022; p. 1 - 27

Rainbow trout (Oncorhynchus mykiss) was introduced in most lakes of Patagonia, generatingconcern about its impact on the receiving communities. However, the information about theeffects of trout in stocked lakes of this region is still fragmentary. We conducted acomprehensive comparative study of fishless and stocked lakes of the arid southern Patagoniato analyze the extent of trout effects on the community composition, primary productivity andfood webs, considering also contrasting climatic conditions (wet and dry years). Rainbowtrout shaped the community of pelagic crustaceans, affecting both species’ dominance andsize structure. Stocked lakes also showed substantial differences in phytoplankton structure,and higher abundances of microplanktonic cyanobacteria, probably caused by top-downeffects. These changes were more pronounced during dry periods, indicating the concomitanteffects of trout introduction and climate fluctuations. Trout also generated alterations in foodwebs, forcing their main prey (amphipods) to shift from predominantly pelagic tobenthic/littoral feeders. Differences in stable isotope values also indicate changes in thehabitat coupling when trout were present. We discuss results from a conservation perspective,considering the potential consequences for waterbirds, mainly for the critically endangeredhooded grebe (Podiceps gallardoi), which have their reproductive habitat in the analyzedaquatic systems.