Theses and Dissertations

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Defense Date

1991

Document Type

Thesis - NSU Access Only

Degree Name

<-- Please Select One -->

Department

Oceanographic Center

First Advisor

Curtis M. Burney

Second Advisor

Charles Messing

Third Advisor

Kathleen Sullivan

Abstract

The diet and feeding habits of the southern stingray, Dasyatis americana, were investigated through aerial surveys, land-based observations, and quantitative analysis of stomach contents. The field research was conducted in the Exuma Cays Land and Sea Park, central Bahamas. Systematic aerial surveys and the land-based observations were made to determine population density and feeding periodicity in terms of time or tidal phase. In August, 1989, systematic surveys were flown over two cays in the Park; a 12 km2 area around Waderick Wells Cay and a 21km2 area around Shroud Cay. Both survey areas were flown three times over different times of the day. Over the large area covered by the aerial surveys the population varied over time of day. A significantly higher density occurred in the morning for both grids and was lowest in the afternoon for both grids suggesting that the stingrays prefer to feed early in the day in the summer. The peak density was 2.07 stingrays per km2 for the Waderick Wells survey area and 1.87 per km2 for the Shroud survey area. A total of 117 hours of land-based observations were made over 4 months; with 28 to 31 hours of observations in April and May 1990 and January and July, 1991. The land-based observations indicated that the stingrays were actively feeding throughout the day, but showed some increase in feeding activity during the high tidal phase. The habitat utilization was recorded during the land-based observations and showed that the stingrays spent most of their time feeding in the soft sediment habitats, thus taking advantage of the soft sediment algal turf and sandy shoal habitats that dominate the shallow marine environments within the Park. Eighteen stingrays were collected in January, 1991 for stomach content analysis. Decapod crustaceans were the most important prey category, but the large number of prey types found in all of the stomachs indicates that the southern stingray is a generalist feeder. There were no empty stomachs and 77% of the stomachs had more than 20 prey items. Stomach fullness measures did not indicate any feeding periodicity. The southern stingray is a generalist feeder taking advantage of a broad range of prey types and opportunistic in its feeding habits, showing no strong feeding periodicity.

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