Abstract
AbstractThe Governments of the Provinces located in Patagonia, Argentina, promote the intensive breeding of salmonids in the Andean Patagonian region. Although annual production is low (450 ton ha–1 year–1), some effects are significant. Waste produced by salmonid breeding (feed losses, faeces and excretion) increases nutrient and organic matter concentrations, which cause modifications of water quality, sediments and biota. A consequent risk is the elevation of eutrophication levels. Possible changes in water composition, sediments, algae and wild fish populations were studied. Sites affected by fish farming showed increased nutrient concentration, and phytoplankton and periphyton biomass. Chlorophyll a was similar at both sites (affected and unaffected by fish farm sites). Sediments clearly reflect fish farm waste inputs: total phosphorus and organic matter increased 12‐fold and fourfold, respectively. The species present in the gill‐net catches were the autochthonous Percichthys trucha, Odontesthes hatcheri, Diplomystes viedmensis, and the introduced salmonids Oncorhynchus mykiss, Salmo trutta, Salmo salar sebago and Salvelinus fontinalis. About 50% of the total catch was salmonids. A major portion of the catch per unit weight was composed of rainbow trout, followed by perch. The catch per unit weight obtained for this reservoir agrees with the range of values previously determined (Quiros 1990) for Patagonian reservoirs. Compared with previous studies by Freyre et al. (1991), a variation in catch composition exists. This consists mainly of an increase in the numbers and condition of O. mykiss and a decrease in P. trucha. Presence of fish that escaped from hatcheries, recognizable by their eroded fins, was observed; particularly in a sampling station near the fish cage systems. Variations in catches could be caused by cyclical changes in fish populations (Wooton 1991), by direct and indirect effects of intensive fish farming, or by a combination of both events, and can only be understood through long‐term studies of catch variation.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
More From: Lakes & Reservoirs: Science, Policy and Management for Sustainable Use
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.