Theses and Dissertations

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Defense Date

11-2007

Document Type

Thesis - NSU Access Only

Degree Name

M.S. Marine Biology

Department

Oceanographic Center

First Advisor

Edward O. Keith

Second Advisor

Lance P. Garrison

Third Advisor

Samuel J. Purkis

Abstract

A series of mass strandings caused by a morbilli virus epizootic in 1987/88 were estimated to have caused the mortality of between 10 and 50 percent of the Atlantic bottlenose dolphin, Tursiops truncatus, population along the Atlantic coast of the United States. In addition, the stranding provided further evidence of two distinct stocks of dolphins, one inshore and one offshore. Subsequently the coastal stock of bottlenose dolphins was declared depleted under the Marine Mammal Protection Act and holds that status today.

From April 1982 to August 1984 aerial sightings were recorded seasonally along the continental shelf from Cape Hatteras, NC to Key West, FL. These data were collected in conjunction with the Southeast Turtle Surveys (SETS) conducted by the National Marine Fisheries Service along random aerial line transects. These datasets were analyzed using the computer program Distance v5.0 to determine population density and abundance across locations, seasons, and years. Covariates, including temperature and sea state, which may affect the ability of observers to sight the dolphins, were considered. Numbers were pooled to determine population abundance prior to the 1987 mass stranding event to determine density change, if any. To visually demonstrate density the sightings and tracklines were mapped using the computer program Global Mapper v7.0.

Results demonstrate the dolphins follow similar migratory patterns as currently observed including a shift of animals north in the summer and south \n the winter. The total abundance of dolphins in this area in the 1980's was significantly (p = 0.0014) less than that found in the 2002 dolphin surveys with a total number in the summer of the early 1980's of 10,102 (CV = 0.1445) and a current estimate of21,527 (CV = 0.2427). In 1995 the Southeast cetacean aerial survey, a replicate study of SETS, was completed in the winter and found 20,005 individuals, a significantly (p = 0.0456) larger number than estimated in SETS. These abundance estimates indicate that the mortality caused by the morbillivirus in 1987/88 did not significantly decrease the overall population of bottlenose dolphins in United States' waters south of Cape Hatteras, NC.

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