Trophic state, fish community and intensive production of salmonids in Alicura Reservoir (Patagonia, Argentina)

Abstract

The 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.

Untitled

“…In this study, our finding suggesting that the total organic substance values at the cage stations (7.02-7.77 %) showed an increase with respect to those at the control stations seems to coincide with the results of different research (Jiwyam and Chareontesprasit, 2001;Temporetti et al, 2001;Alpaslan and Pulatsü, 2008;Rooney and Podemski, 2010).…”

Native and exotic fishes in a Patagonian reservoir with rainbow trout cage culture: spatial and trophic resource use

“…Wild and farmed rainbow trout were identified according to their external characteristics (Temporetti et al, 2001;Fiske et al, 2005). However, since previous studies in Chilean Patagonia have found that ERTand WRTcan exhibit no obvious phenotypic differences (Consuegra et al, 2011), estimated abundances of ERT in the present study are probably underestimated (conversely, diet overlap between ERT and WRT may be overestimated).…”

“…Considering that the abundance and growth of Daphnia in Patagonian lakes is limited mainly by phosphorous (Balseiro et al, 2007), our fish stomach content data suggest an increase in the availability of this crustacean in the Alicurá reservoir, which may be a delayed consequence of nutrient discharges from aquaculture activities (Temporetti et al, 2001).…”

“…This pattern was pronounced close to the farms (Temporetti et al, 2001), with highly fluctuating abundance between years, probably reflecting massive escape events .…”

Rainbow Trout (<i>Oncorhynchus mykiss</i>) Cage Culture: Preliminary Observations of Surface Sediment’s Chemical Parameters and Phosphorus Release in Gokcekaya Reservoir, Turkey

“…The effect on the sediment of a cage culture with a production capacity of 450 t•y −1 (cage production started in 1986) in Alicura Reservoir was examined by [21]. Comparing sediment TP and TN concentrations, the increase in TP was found to be higher than TN, similar to [20].…”