1. Salmon and Freshwater Team, Cefas, Pakefield Road, Lowestoft, Suffolk NR33 OHT, UK.
2. Department of Zoology and Ecology, School of Sciences, University of Navarra, Irunlarrea 1, E-31008 Pamplona, Spain.
3. Centre for Conservation Ecology and Environmental Change, Bournemouth University, Poole, Dorset, UK; Environmental and Life Sciences Graduate Program, Trent University, Peterborough, Ontario, Canada.