1. Institute of Biological and Environmental Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, UK
2. MSS Marine Laboratory, PO Box 101, Victoria Road, Aberdeen AB11 9DB, UK
3. Computer Vision and Robotics Group, Universitat De Girona, Campus Montilivi, Edifici P-IV, Girona 17071, Spain
4. IMARES, Wageningen UR, Haringkade 1, P.O Box 68, 1970 AB IJmuiden, the Netherlands