1. School of Aquatic and Fishery Sciences; University of Washington; Seattle WA 98195 USA
2. CSIRO Oceans and Atmosphere; GPO Box 1538 Hobart TAS 7001 Australia
3. Marine Resource Assessment and Management Group (MARAM); Department of Mathematics and Applied Mathematics; University of Cape Town; Rondebosch 7701 South Africa
4. CEFAS Lowestoft Laboratory; Pakefield Road Lowestoft Suffolk NR33 0HT UK