N1 - Funding Information: *Thanks are due Richard Carson, Ron Cummings, Glenn Harrison, Ray Kopp, Stanley Presser, and Pam Rathbun for comments or suggestions about related research, to two anonymous referees for very helpful reviews, and to Kris McGee and Kelly DeMarchis for preparing several versions of this paper. Smith is a Resources for the Future University Fellow and his research was partially supported by the UNC Sea Grant Program project number R/MRD-32.