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.
Department of Fisheries and Oceans Canada, St. Andrews Biological Station 531 Brandy Cove Road, St. Andrews, New Brunswick, E5B 2L9, Canada. gregor@uoguelph.ca
Gregor K
GK
Reid
Richard D
RD
Moccia
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