BLUEBACK HERRING (ALOSA-AESTIVALIS) IN LAKE ONTARIO - FIRST RECORD, ENTRY ROUTE, AND COLONIZATION POTENTIAL

Two juvenile blueback herring (Alosa aestivalis) were caught in Lake O ntario in October 1995 the first record of this anadromous marine clup eid in the Great Lakes. Blueback herring most likely gained entry to L ake Ontario via the Erie Barge Canal, a navigation canal that links th e Mohawk-Hudson rivers, which drain to the Atlantic Ocean, to Oneida L ake, which drains to Lake Ontario through the Oneida-Oswego rivers. Bl ueback herring ascend the Hudson River to spawn and were first reporte d from the upper Mohawk River in 1978. They currently spawn in several of the upper Mohawk's tributaries, including one about 430 km from th e ocean but only 25 km fp om Oneida Lake. They were first found in One ida Lake in 1982 and, in fall 1994, large numbers of juvenile blueback herring were found moving down the Oswego River. In the southern Unit ed States, blueback herring established self-reproducing populations i n several reservoirs, and thus they have the potential to colonize Lak e Ontario. If blueback herring became established in Lake Ontario, the y could spread to other Great Lakes and impede recovery of depressed p opulations of indigenous fishes, like lake herring (Coregonus artedi) and lake trout (Salvelinus namaycush), through competition with, or pr edation on, their larvae.