Oceanic migration rates of Upper Chesapeake Bay striped bass ( Morone saxatilis ) , determined by otolith microchemical analysis

As an estuarine-dependent species, striped bass (Morone saxatilis) demonstrate large plasticity in migration patterns (Secor and Piccoli, 1996). Striped bass in Chesapeake Bay are partial migrants; only a fraction of individuals will leave estuarine habitats for oceanic waters (Kohlenstein, 1981). Never the less, Chesapeake Bay striped bass are the major contributors to interjurisdictional ocean fisheries (Merriman, 1941; Wirgin et al., 1993). Rates of contributions by Chesapeake Bay striped bass to those fisheries are determined by lifetime patterns of habitat use, ontogenetic rates of egress from Chesapeake Bay, and regional rates of exploitation and natural mortality (Dorazio et al., 1994). Rates of oceanic residence have been shown to vary by sex and increase with age. Analyzing striped bass tagged in the Potomac River, Kohlenstein (1981) advanced the working hypothesis that young striped bass remain in or near the tributary in which they were spawned for two or three years. At this point a substantial proportion of immature females (ca. 50%) emigrate from the Bay, remaining in ocean waters until sexually mature (age 5−7 years). In contrast, males are mature by age 2 but remain in the Bay throughout their lives. This hypothesis remains untested, although substantial deviation from this proposed pattern is indicated by tagging studies and catch records. Oceanic migration rates of Upper Chesapeake Bay striped bass (Morone saxatilis), determined by otolith microchemical analysis*