LE3 .A278 1986

1986

Daborn, Graham

Acadia University

Master of Science

Masters

Biology

Biology

The diet of summer resident alewives (Alosa pseudoharengus) and blueback herring (Alosa aestivalis) obtained from brush weir and drift gill net collections in Minas Basin from June to September, 1983, was analyzed using number, volume and frequency of occurrence methods. Age composition, maturity, length-weight relationships and growth characteristics were also examined. Feeding occurred over the diel and mtidal cycles and both species showed considerable overlap in their diet. Alewives favored larger, more benthic prey (e.g. amphipods, mysids, crangonid) while blueback herring appeared to concentrate their feeding on microzooplankters (e.g. calanoid copepods, cypris larvae, molluscan veligers). Differences in prey suggest that alewives frequently inhabit the lower portion of the water column, while blueback herring utilize the upper part of the water column. Yearling individuals of both species favored a more planktonic diet than older fish. Corophium volutator was the single most important prey item, particularly in alewives. The Five Islands region appears to be an important foraging area for both species while feeding activity in Cobequid Bay is greatly reduced. Both species may feed more extensively outside of Cobequid Bay where water temperatures are lower and food is more abundant and decrease their feeding activity in the upper reaches of the Bay where food is less abundant.

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