On the Proportion of the Chesapeake Bay Stock of Striped Bass That Migrates into the Coastal Fishery

Past observations of year-class patterns and racial characteristics of striped bass (Morone saxatilis) indicate that the Chesapeake Bay spawning grounds provide the principal support of the Atlantic coastal fishery for this species. Past tagging studies have suggested that only a few percent of the striped bass leave the bay, but a few percent of the Chesapeake Bay stock could not support the coastal fishery. To resolve this contradiction, I reexamined tagging studies conducted during 1957–1961 in the Potomac River using recent data on age-specific sex ratios at several positions in the river. For 3-year-olds, the proportions of tag returns from outside the bay were linearly related to the female proportion of the stock in the tagging area. The analysis indicates that few young males leave the bay and approximately one-half of the 3-year-old females migrate to coastal waters. A similar estimate that 50% of age-III females migrate from the bay was independently derived from age-specific sex ratios in Chesapeake Bay in fall 1976, coupled with sex-specific estimates of spring fishing mortality. Smaller proportions of age-II and age-IV females leave the bay. This level of migration could support the majority of the coastal striped bass fishery.