EFFECTS OF ENVIRONMENTAL-FACTORS ON ICHTHYOPLANKTON COMMUNITIES IN THE MIRAMICHI ESTUARY, GULF OF ST-LAWRENCE

Ichthyoplankton in 20 taxa (17 identified to species, three to genus) representing 14 families were collected in 10 surveys of the Miramichi estuary between May and September 1992. The taxonomic composition was typical of other estuaries in the Gulf of St Lawrence and Gulf of Mai ne. Larvae of three anadromous species [rainbow smelt (Osmerus mordax) , alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivali s)] were several orders of magnitude more abundant than any other taxo n. The upper estuary (Miramichi River and its tributaries) probably se rves as a nursery ground for larvae of these species and others such a s Atlantic tomcod (Microgadus tomcod). The species composition of the lower estuary (Miramichi Bay) was dominated by typically marine forms and probably serves as a nursery ground for winter flounder (Pleuronec tes americanus), smooth flounder (Pleuronectes pulnami), sculpin (Myox ocephalus sp.) and sand lance (Ammodytes sp). Of the environmental fac tors investigated, salinity was the most useful predictor of larval di stribution in the estuary.