Monitoring the environmental impacts and consent compliance of freshwater fish farms

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 land-based 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.