1. Organismic and Evolutionary Biology Program, University of Massachusetts Amherst, 230 Stockbridge Road, 204C French Hall, Amherst, MA 01003, USA.
2. US Geological Survey, Leetown Science Center, S.O. Conte Anadromous Fish Research Center, One Migratory Way, Turners Falls, MA 01376, USA.
3. School for Marine Science and Technology, University of Massachusetts Dartmouth, 836 S. Rodney French Blvd., New Bedford, MA 02744, USA.