Natural Sources and Requirements of Phosphorus for Fishes

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Abstract
The hypothesis that daily consumption of natural prey provides a source of phosphorus sufficient to meet growth and metabolic requirements of fishes is examined. Fish may be capable of utilizing available phosphorus directly from the water; however, this source is negligible in comparison to dietary intake. Experiments were designed to test the effect of different dietary phosphorus levels, chosen to approximate those of natural prey items, on growth of juvenile perch at temperatures encountered during the growing season. Rations were based upon estimates of daily food consumption for perch in Lake Memphremagog. Growth was significantly temperature-dependent and independent of dietary phosphorus levels. Phosphorus:ash ratios of whole fish were not significantly different among diet treatments or between the initiation and termination of the growth experiment. Excretion of phosphorus was positively related to phosphorus intake.Key words: absorption efficiency, daily ration, growth, Lake Memphremagog, nutrition, Perca flavescens, phosphorus budget, yellow perch