Waste loadings from a freshwater Atlantic salmon farm in Scotland

Recent studies suggest that waste generation from the freshwater phase of Atlantic salmon (Salmo solar L.) production varies considerably on an annual basis. A fish farm on the West Coast of Scotland was visited regularly during a two-year period to determine inflow and outflow water quality. Waste output budgets of suspended solids (SS), biochemical oxygen demand (BOD), total nitrogen (TN), total phosphorus (TP), total ammonia nitrogen (TAN = NH₃+NH₄⁺), dissolved reactive phosphorus (DRP) and total phosphorus (TP) were produced. The annual waste loadings obtained were 71 kg TN t fish^-1 yr^-1 (one year of data only), 10.911.1 kg TP t fish^-1 yr^-, 1.2-2.1 kg DRP t fish^-1 yr^-1, 422-405 kg BOD₅ t fish^-1 yr^-1, 327-337 kg SS t fish^-1 yr^-1, and 30-35 kg TAN-N t fish^-1 yr^-1. Simple linear regression models relating waste parameter production to water temperature and feeding regime were developed. When compared to existing data for other salmonid production systems, greater ranges of daily waste loadings were observed. Wide variations in concentrations of these parameters during a daily cycle were also observed, suggesting that mass balance estimates of waste production will provide more robust estimates of waste output than frequent monitoring of outflow water quality.