1. Department of Biology, Division of Zoology, University of Oslo, Post Office Box 1050 Blindern, N-0316 Oslo, Norway.
2. Department of Coastal Zone Studies, Institute of Marine Research, Flødevigen Marine Research Station, N-4817 His, Norway.
3. Institute of Marine Research, Post Office Box 1870 Nordnes, N-5024 Bergen, Norway.
4. National Center for Atmospheric Research, Boulder, CO 80307, USA.
5. Department of Statistics and Actuarial Science, University of Iowa, Iowa City, IA 52242, USA.
6. Center for Advanced Studies in Ecology and Biodiversity, Pontificia Universidad Católica de Chile, Post Office Box 114-D, Santiago CP 6513677, Chile.