FEEDING AND ASSIMILATION OF <i>MYSIS RELICTA</i>1,2

Abstract

Feeding habits and assimilation efficiencies were studied for Mysis relicta from Char Lake, N.W.T., and Stony Lake, Ontario. Stony Lake animals were rather voracious predators, feeding on Daphnia and other cladocerans during their vertical migration at night. Char Lake mysids fed primarily on diatoms and inorganic particles on a moss substrate. The gravimetric method showed an assimilation efficiency of 85% for Stony Lake mysids feeding on Daphnia pulex ; the Conover ash‐ratio method showed 52%. Results of the ashratio method corrected for ash assimilation, using the gravimetric data, gave an assimilation efficiency of 87%, indicating that ash assimilation can account for the difference between the two methods. A negative assimilation efficiency was obtained by the ash‐ratio method for Char Lake mysids feeding on moss washings, suggesting that mysids may be able to select organic material from the substrate.