WASTE LOADINGS FROM A FRESH-WATER ATLANTIC SALMON FARM IN SCOTLAND

Recent studies suggest that waste generation from the freshwater phase of Atlantic salmon (Salmo salar L.) production varies considerably on an annual basis. A fish farm on the West Coast of Scotland was visite d regularly during a two-year period to determine inflow and outflow w ater quality. Waste output budgets of suspended solids (SS), biochemic al oxygen demand (BOD), total nitrogen (TN), total phosphorus (TP), to tal ammonia nitrogen (TAN = NH3+NH4+), dissolved reactive phosphorus ( DRP) and total phosphorus (TP) were produced. The annual waste loading s obtained were 71 kg TN t fish(-1) yr(-1) (one year of data only), 10 .9-11.1 kg TP t fish(-1) yr(-1), 1.2-2.1 kg DRP t fish(-1) yr(-1), 422 -485 kg BOD5 t fish(-1) yr(-1), 327-337 kg SS t fish(-1) yr(-1), and 3 0-35 kg TAN-N t fish(-1) yr(-1). Simple linear regression models relat ing waste parameter production to water temperature and feeding regime were developed. When compared to existing data for other salmonid pro duction 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 wa ste production will provide more robust estimates of waste output than frequent monitoring of outflow water quality.