Date of Award
2000
Degree Type
Thesis
Degree Name
Master of Science in Oceanography
Department
Oceanography
First Advisor
Robert Kenney
Abstract
The population of harbor seals has increased in Maine and Massachusetts since bounty hunting was discontinued in the 1960s and the advent of the Marine Mammal Protection Act in 1972. Little is known about the migrant population of harbor seals in southern New England. Until recently, only one long-duration census survey and occasional counts have recorded the number of harbor seals in Rhode Island waters. Since 1993, regular surveys of the locations where harbor seals come ashore or haul out semi-diurnally have provided the first estimates of local harbor seal abundance and distribution.
The western Atlantic harbor seal, Phoca vitulina concolor, seasonally moves into the primary marine bodies of water in Rhode Island, Rhode Island and Block Island Sounds and Narragansett Bay, arriving in late September and departing by mid-May. The number of seals does not increase in a linear fashion throughout the sighting season, as was expected from migration trends in southeastern Canada. The typical seasonal distribution pattern of harbor seal occurrence is a gradual increase in the fall and early winter followed by a rapid rise in seal numbers, a peak, and sudden decline in the number of harbor seals. The number of seals always rapidly declines from mid-or late April to early May by mid-May few seals remain in Rhode Island waters.
The geographic distribution of seals has changed over the last 13 years. The number of locations where seals come ashore has more than tripled, yet some of the traditional sites have been abandoned. Twenty-seven harbor seal haul outs have been identified throughout Narragansett Bay and surrounding the perimeter of Block Island. Over the last three decades, Rhode Island has experienced a significant increase in the number of harbor seals now found here. Since the late 1960s, the number of harbor seals has increased by a factor of ten, and it has nearly quadrupled since 1987. In 1999, 349 seals were counted in Rhode Island for an abundance estimated at 825-1,047 harbor seals.
Recommended Citation
Schroeder, Cheryl L., "Population Status and Distribution of the Harbor Seal in Rhode Island Waters" (2000). Open Access Master's Theses. Paper 2465.
https://digitalcommons.uri.edu/theses/2465