1. Polar Research Center, Korea Ocean Research and Development Institute, Ansan, PO Box 29, Seoul, 425–600, Korea,
2. Chesapeake Biological Laboratory, University of Maryland System, Center for Environmental and Estuarine Studies, Solomons, MD 20688–0038, USA,
3. Department of Marine Production Management, College of Fisheries Science, Pukyong National University, Pusan, 608–737, Korea