1. Department of Fisheries Science, Virginia Institute of Marine Science, College of William & Mary, Rt 1208 Greate Road, Gloucester Point, VA 23062, USA
2. Cooperative Marine Education and Research Program, Northeast Fisheries Science Center, National Marine Fisheries Service, NOAA, Woods Hole, MA 02543, USA
3. Department of Cell and Organism Biology, Vision Group, Lund University, Lund, Sweden