1. Department of Biology, Dalhousie University, 1355 Oxford Street, Halifax, NS B3H 4R2, Canada
2. Marine Affairs Program, Dalhousie University, 1355 Oxford Street, Halifax, NS B3H 4R2, Canada
3. Institute of Marine Research, FlØdevigen Marine Research Station, N-4817 His, Norway
4. Centre for Coastal Research, University of Agder, N-4606 Kristiansand, Norway