[1] Fisheries & Oceans Canada, Pacific Biol Stn, 3190 Hammond Bay Rd, Nanaimo, BC V9T 6N7, Canada
[2] Univ Alberta, Dept Biol Sci, Edmonton, AB T6G 2E9, Canada
[3] Penn State Univ, Dept Biol, University Pk, PA 16802 USA
[4] Fisheries & Oceans Canada, Inst Ocean Sci, 9860 West Saanich Rd, Sidney V8L 5T5, BC, Canada