1. Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, P. O. Box 38, 146 Williams Street, Solomons, MD 20688, USA
2. National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Southeast Fisheries Science Center, Beaufort Laboratory, 101 Pivers Island Road, Beaufort, NC 28516, USA
3. National Marine Fisheries Service, Northeast Fisheries Science Center, Oceanography Branch, 28 Tarzwell Drive, Narragansett, RI 02882, USA