1. Fisheries and Oceans Canada, 1 Challenger Drive, Dartmouth, NS B2Y 4A2, Canada.
2. Biology Department, Dalhousie University, 1355 Oxford Street, Halifax, NS B3H 4J1, Canada.
3. Biology Department, Acadia University, 33 Westwood Avenue, Wolfville, NS B3P 2R6, Canada.