Distribution, Localized Abundance, Movements, and Migrations of Juvenile Sandbar Sharks Tagged in Delaware Bay
Camilla T. McCandless, Harold L. Pratt, Jr., Nancy E. Kohler, Rebeka R. Merson, and Conrad W. Recksiek
Abstract.—Delaware Bay is one of two principal nursery grounds for the sandbar shark Carcharhinus plumbeus in United States coastal waters, with the second one located in Chesapeake Bay. Tagging studies were conducted for juvenile sandbar sharks in Delaware Bay during their summer nursery seasons from 1995 to 2000 using gill-net (1995–2000) and longline (1997–2000) gears. These studies were designed to aid fishery managers in defining essential fish habitat for juvenile sandbar sharks tagged in Delaware Bay by determining spatial and temporal distributions, overwintering grounds, and philopatry to natal nursery areas. A total of 2,066 juvenile sandbar sharks were caught in Delaware Bay from 1995 to 2000, and 87% of the sharks sampled were tagged before release. Of these tagged sharks, 156 (9%) have been recaptured through 2005. Juvenile sandbar sharks were most abundant along the Delaware coast, with more localized abundances on the shoal areas throughout the bay. Recaptures indicate that the majority of sandbar sharks born in Delaware Bay return to their natal nurseries for up to 5 years following birth (and potentially up to 12 years of age), overwinter off North Carolina, and eventually expand their range south to the east coast of Florida and into the Gulf of Mexico as they get larger. This study also provides the first evidence of mixing between the juvenile sandbar shark populations of Delaware and Chesapeake Bays during the summer nursery season.