Ontogenetic diet shifts in age-0 striped bass, Morone saxatilis, from the Miramichi River estuary, Gulf of St. Lawrence

Abstract

Stomach contents of 2928 age-0 striped bass, Morone saxatilis (2.9–153.3 mm total length (TL)), collected from June to November 1992 in the Miramichi River estuary were examined. Seventy-seven percent of the fish stomachs examined contained food organisms and 34 prey taxa were identified. Larval striped bass (< 25 mm TL) fed primarily on immature and adult copepods. The onset of exogenous feeding correlated both spatially and temporally with a peak in the abundance of prey. Chesson's α index indicated progressive selection of larger prey with increasing size of larval striped bass, from small rotifers to larger calanoid copepods to the relatively large calanoid Eurytemora sp. Mysids (Neomysis americand) and sand shrimp (Crangon septemspinosa) were the principal prey of striped bass > 50 mm TL. Contributions by other prey groups (molluscs, polychaetes, amphipods, insects, and larval fish) were minor. Large underyearlings, 64–84 mm TL, in near-fresh water ate proportionally more mysids than fish downriver in more saline waters. Feeding ceased when water temperatures declined below about 3 °C in November.