Population and Energy Dynamics of Trout Salmo trutta in a Small Danish Stream

Abstract

SUMMARY (1) Data on population size, growth, production and food consumption of trout, Salmo trutta, in a small Danish stream were obtained from March 1974 to April 1976. Annual production in the 2 years was 88.9 (95% C.L. 82.6-97-4) and 65.8 kJ m-2 (95% C.L. 60.8-73.1), respectively, and the maximum rate of production coincided with the period of maximum growth rates. (2) Food consumption was estimated from: (a) equations based on observed growth rates and experimental data on growth and food consumption (Cactual) and (b) Winberg's balanced equation based on approximation of the standard metabolic rate (CwinII). The equation relating standard metabolic rate to body weight, Rs = aW', was determined from experiments on oxygen consumption at different temperatures. The k estimate of 0.93 differed significantly from the general value of 0.76 suggested by Winberg but was not different from published values for brown trout. For comparative purposes the food consumption, CwinnII and CwinII2, based on k = 0.93 and k = 0.76, respectively, was estimated. The annual food consumption in each of the 2 years was Cactual; 479.2 (range 448.3-521-9) and 369.8 kJ m-2 (range 343.5-406-8), CwinII,: 784.2 (range 738.6-851-6) and 609.4 kJ m-2 (range 574.7-664-9) and CWinI12: 619.6 (range 579.7-674-6) and 481.1 kJ m-2 (range 447.7-529-0). (3) The Cactual, CwinIIi and CWinIx2 values differed significantly. It is emphasized that