Estimating aquatic phosphorus concentrations 30 metres down-current from a rainbow trout cage array.
Aquatic total phosphorus (Tot-P) is measured 30 m distant from rainbow trout (Oncorhynchus mykiss) cages, for regulatory compliance on the Canadian side of Lake Huron. The ability to predict changes in near-field Tot-P concentrations from changes in production, or to explain near-field concentrations in the event of compromised reference sites, would be very useful for managers and farmers. A logical first step in the development of a near-field model is the estimation of down-current Tot-P concentrations. A nutritional mass balance approach was used to calculate the amount of non-settleable Tot-P which was divided by the corresponding flushing volume over four separate production periods. Despite a number of uncertainties, such as cage effects on flushing volume, the contribution of particulate phosphorus, fish distribution, feed conversion ratio, and ingestion-excretion time; accuracy (slope = 1.06) and precision (r(2) = 0.75) of modelled estimates fit well with empirical results. It was concluded that 30 m down-current Tot-P concentrations could be modelled under a diverse set of culture and environmental conditions, suggesting typical 'near-field' concentrations of Tot-P can be explained on the basis of farm activities.
Reid
Gregor K
GK
Department of Fisheries and Oceans Canada, St. Andrews Biological Station 531 Brandy Cove Road, St. Andrews, New Brunswick, E5B 2L9, Canada. gregor@uoguelph.ca
Moccia
Richard D
RD
D000818:Animals; D017756:Aquaculture; D004784:Environmental Monitoring / Q000379:methods*; D017686:Oncorhynchus mykiss; D010758:Phosphorus / Q000032:analysis*; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*
D014874:Water Pollutants, Chemical; D010758:Phosphorus