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Aquaculture Environment Interactions

    AEI prepress abstract   -  DOI:

    Relationship between salt use in fish farms and drift of macroinvertebrates in a freshwater stream

    Francisco Encina-Montoya, Luz Boyero, Alan M. Tonin, MarĂ­a Fernanda Aguayo, Carlos Esse, Rolando Vega, Francisco Correa, Carlos Oberti, Jorge Nimptsch*

    *Corresponding author:

    ABSTRACT: Salmon fish farms utilize 20–30 t yr-1 salt (NaCl) to prevent and control fungal infections; increasing salinity has potentially adverse effects on freshwater biodiversity and ecosystem functions and services. We studied the effects of fish-farm effluents on benthic macroinvertebrate communities in a northern Patagonian stream (Chile), where the aquatic biota community has not been previously exposed to osmotic stress due to natural low-conductivity conditions. Benthic samples were collected at 3 sites at a land-based salmon aquaculture facility (one located 100 m upstream from the fish-farm effluent, 2 sites located 200 and 400 m downstream from the same effluent, respectively). We found changes in benthic macroinvertebrate communities downstream from the effluent that had higher abundances of tolerant taxa and lower abundances of sensitive taxa, this pattern was related to nutrient and salt concentration in water. We also studied the effects of salinity on macroinvertebrate drift in a mesocosm experiment conducted in recirculating channels, measuring drift of 2 salt-sensitive macroinvertebrates (Andesiops peruvianus and Smicridea annulicornis) after exposure to different salinity pulses fish-farm discharge patterns. Our results demonstrate that (1) fish-farm effluents can alter stream macroinvertebrate community composition and dynamics, and (2) such effects are at least partly driven by high salt concentrations in effluent waters.