Abundance of native fishes, wild‐introduced salmonids and escaped farmed rainbow trout in a Patagonian reservoir

Abstract

The introduction of salmonids in Patagonia has resulted in significant impacts on its lakes, as well as a major impact on streams, in which native fishes seem to have been displaced almost completely by rainbow trout (Oncorhynchus mykiss). Another perspective is that the introduced salmonid species have resulted in wild fish populations that sustain an economically important sport fishery. The wide distribution and high abundance of escaped farmed rainbow trout, and a clear decrease in the abundance of native and successfully introduced salmonid species in Alicura Reservoir were all observed, based on comparison of recent data and data from 1993 to 1995 corresponding to littoral gillnet captures. Thus, both native fish and introduced salmonid populations seem to have been drastically reduced in the presence of farmed fish escapees. The results of the present study regarding fish escapes deserve major consideration when making decisions about fish cage culture activities for other Patagonian reservoirs.

Traditional Mapuche ecological knowledge in Patagonia, Argentina: fishes and other living beings inhabiting continental waters, as a reflection of processes of change

“…The salmonids represent a complex problem in that they have a positive impact on regional economy, but generate substantial negative effects in the environment [5–7]. The rainbow trout in particular, despite being a species of great sport value in Patagonia and the most commonly used species in commercial aquaculture [90], has generated significant negative effects in the population of native fishes [7, 135, 136]. …”

Freshwater fishes of Patagonia: conservation and fisheries

“…Salmonid aquaculture has developed into a highly globalized trade‐dependent industry, where fish meal and fish oil, produced in fisheries around the world, are key inputs to produce the feed for farmed fishes, transforming schooling fishes into salmonids flesh (Deutsch et al ., ). Although salmonid cage culture in Patagonian reservoirs is subjected to the negative effects of global warming (Báez et al ., ), O. mykiss farming activities have increased and impose the threat of fish escapes both on native fish populations and on the wild salmonid sport fishery (Cussac et al ., ). The impacts may not only be in the reservoirs where the farms are placed ( e.g .…”

“…Dams are frequently accompanied by fish culture cages and fish culture usually involves fish escapes. Escaped fishes not only affect fish population in the same reservoir, but also their consequences may be observed at headwater lakes and rivers (Cussac et al ., ).…”

Conservation of the freshwater fauna of Patagonia: an alert to the urgent need for integrative management and sustainable development

“…First of all, aquaculture based on salmonid production is a severe stressor in Patagonia. In Chile, this activity is advancing dramatically southward, increasing the input of nutrients, antibiotics and other drugs into aquatic ecosystems, as well as extending the propagule pressure of salmonid invasion due to the escape of millions of individuals from farms every year (Cussac et al, ). Similar to aquaculture, hydropower development is an additional major stressor in Patagonia.…”