[1] Univ Oslo, Dept Biol, CEES, N-0316 Oslo, Norway
[2] Inst Marine Res, N-5817 Bergen, Norway
[3] Ontario Minist Nat Resources, Aquat Res & Dev Sect, Peterborough, ON K9J 7B8, Canada
[4] Univ Bergen, Dept Biol, N-5020 Bergen, Norway
[5] Int Inst Appl Syst Anal, Evolut & Ecol Program, A-2361 Laxenburg, Austria