Monitoring the environmental impacts and consent compliance of freshwater fish farms

Abstract

Strategies for monitoring the chemical and biological impacts of freshwater land-based and cage fish farms in the West of Scotland are described and the results of monitoring are presented. The compliance of landbased farms with discharge consents is discussed. The impact of fish farming on receiving water chemistry was found to be limited, but effects on benthic invertebrate communities in both running waters and lochs were more readily detectable, although generally localized in the immediate vicinity of the farm. The benthic fauna of a stream receiving wastes from a land-based farm recovered within 19 months of the discharge ceasing. At a vacated cage site in a loch, severe impact on the sediments was still evident after more than 3 years. Problems in monitoring for consent compliance are discussed and the need for closer liaison between the industry and regulatory bodies is emphasized.

Tracing dissolved organic matter (DOM) from land-based aquaculture systems in North Patagonian streams

“…These results are supported by previous studies, where bacteria downstream of fish farm outflows showed much higher densities and heterotrophic activity due to the accumulation of generated organic matter (Boaventura et al, 1997;Carr and Goulder, 1990). Moreover, the presence of occasionally large mats of sewage fungus and bacteria downstream of the Molco Aquaculture effluent reinforces that the enhanced DOM concentration downstream of Molco Aquaculture (and the other studied fish farms) also increases the microbial respiration of the receiving stream, as clearly shown by Doughty and McPhail (1995) for similar Scottish aquaculture systems.…”

“…This may result in a complete shift of species in all large groups when comparing stretches up-and downstream of land-based aquacultures. This biotic effect has been documented by Doughty and McPhail (1995), showing changes in benthic invertebrate communities downstream of aquaculture effluents in fluvial ecosystems.…”

Reduction in effluent nutrient loads from flow-through facilities for trout production: a review

“…Cold water stream ecosystems can show a typical reaction or shift in the river continuum when disturbed by nutrient‐rich trout farm effluents (Loch, West & Perlmutter 1996). Effluents with high organic loads [biological oxygen demand in 5 days (BOD 5 )>2.1 mg L −1 ] show, in the vicinity of the discharge point (maximum 100 m), a dominance of heterotrophic bacteria and sewage fungi suppressing the primary production (Doughty & MCPhail 1995; Loch et al 1996; Villanueva, Queimalinos, Modenutti & Ayala 2000). The heterotrophic dominance is followed by an increased primary production measured as chlorophyll a .…”

“…The heterothrophic and euthrophic change is often accompanied by a shift in the macroinvertebrate community, from intolerant, oligosaprobic species upstream the discharge point, to nutrient‐tolerant species, indicating an ecosystem degradation (Camargo 1994; Doughty & McPhail 1995; Loch et al 1996; Selong & Helfrich 1998). The macroinvertebrate community needs the longest distance from the point source for recovery.…”

Impacts of Trout Culture Effluent on Water Quality and Biotic Communities in Virginia Headwater Streams

“…Aquaculture effluents can affect downstream macroinvertebrate and fish communities. Intolerant Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa generally decrease, whereas tolerant taxa (Diptera, Gastropoda, Hirudinea, Oligochaeta) increase (Carmago 1992;Doughty and McPhail 1995;Henderson and Ross 1995;Loch et al 1996). Fish biomass may increase with nutrient enrichment because of enhanced primary production and macroinvertebrate biomass (Rasmussen 1986).…”