Food habits of larval and juvenile anadromous alewives, Alosa pseudoharengus (Wilson), in Lake Ainslie, Nova Scotia, 1979

Gut analysis was performed on 60 larvae ( 5.3 - 19.0mm FL ) and 170 juveniles ( 19.1 - 58.5mm FL ) of an anadromous population of alewife, Alosa pseudoharengus ( Wilson ), in Lake Ainslie, Cape Breton, Nova Scotia, from May 20 - August 23, 1979. Food habits were examined with respect to size and sample date. Ivelev's Electivity Index was used to determine the feeding selectivity for available zooplankton. The most important food organisms in the zooplankton were the cladocerans Bosmina sp. and Daphnia retrocurva and the copepod Diaptomus minutus. Adult dipteran and ephemeropteran insects formed a significant amount of the total food ration at the beginning of July and through August. On August 23 their contribution was 82.6% of the dry weight biomass. Ostracods, amphipods, and chironomid ( Diptera ) larvae formed a significant part of the diet at times. The degree of fullness of the gut was found to be dependent on the time of capture. The frequency of "empty" stomachs was significantly higher in the late morning and late afternoon. Morphological changes in the gill rakers with growth were examined. The number of rakers/mm was found to be in a negative exponential relationship with respect to fork length.