Date of Award
Master of Science in Coastal Marine and Wetland Studies
Coastal and Marine Systems Science
Robert F. Young
John J. Hutchens, Jr.
National Marine Fisheries Service (NMFS) stock assessment reports describe two coastal and two estuarine bottlenose dolphin stocks that utilize the waters of northern South Carolina (Waring et al. 2014), but coastal data from this area are lacking. Photo-ID mark-recapture surveys were conducted from 2013-2015 along two 50 km coastal transects centered on Murrells Inlet, SC; and from 2014-2015 along two 50 km transects covering both coastal and estuarine waters centered on Little River, SC. Capture histories of marked individuals were used to estimate abundance and, in conjunction with neighboring catalog comparisons, infer movements, residency patterns, and stock membership. Local abundance estimates derived from the Markovian Mt model (MARK 6.2) varied seasonally and inter-annually. The most reliable abundance estimates are from the 2013 and 2014 summers (371 and 1441, CV 0.17 and 0.14, respectively). Lack of recaptures and low distinctive rates caused an upward bias for estimates in the other seasons. Decreased winter abundance was reflected in our data by a 2-fold decrease in sightings-per-unit-effort (SPUE) from summer to winter. The fall migratory peak attributed to the Southern Migratory Coastal Stock was reflected by a 2-fold increase in SPUE between summer and fall. A likely shift in stock composition occurred between summer and fall given the lack of recaptures. Members of the Northern South Carolina Estuarine System Stock were sighted in coastal waters as far north as Murrell’s Inlet, supporting NMFS definitions; but several members of the Southern North Carolina Estuarine System Stock were sighted in coastal waters 70 km south of their currently defined southern boundary, potentially warranting a revision. Dorsal fin matches among several catalogs indicate that multiple stocks overlap in northern South Carolina and that an undefined coastal stock occurs from southern North Carolina to northern South Carolina, possibly as far north as Cape Lookout, NC and as far south as Charleston, SC in the summer.
Silva, Daniela C., "Use of Photo-identification and Mark-recapture Techniques to Identify Characteristics of the Stock Structure of Coastal Bottlenose Dolphins (Tursiops truncatus) Off Northern South Carolina" (2016). Electronic Theses and Dissertations. 46.