TRENDS IN MANATEE (TRICHECHUS MANATUS LATIROSTRIS) COUNTS AND HABITAT USE IN TAMPA BAY, 1987–1994: IMPLICATIONS FOR CONSERVATION

Authors

  • Irene E. Wright,

    1. Florida Fish and Wildlife Conservation Commission, Florida Marine Research Institute, 100 8th Avenue SE, St. Petersburg, Florida 33701, U. S. A. E-mail: baswright@aol.com
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    • 1

      Current address: 250 Harbour Town Drive, Madison, WI 53717, U. S. A

  • John E. Reynolds III,

    1. Eckerd College, 4200 54th Avenue S., St. Petersburg, Florida 33711, U. S. A.
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    • 2

      Current address: Mote Marine Laboratory, 1600 Thompson Parkway, Sarasota, FL 34236, U. S. A.

  • Bruce B. Ackerman,

    1. Florida Fish and Wildlife Conservation Commission, Florida Marine Research Institute, St. Petersburg, Florida 33701, U. S. A.
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  • Leslie I. Ward,

    1. Florida Fish and Wildlife Conservation Commission, Florida Marine Research Institute, St. Petersburg, Florida 33701, U. S. A.
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  • Bradley L. Weigle,

    1. Florida Fish and Wildlife Conservation Commission, Florida Marine Research Institute, St. Petersburg, Florida 33701, U. S. A.
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    • 3

      Current address: Greenhorne and O'Mara, 9800 4th Street North, St. Petersburg, FL 33702, U. S. A.

  • William A. Szelistowski

    1. Eckerd College, 4200 54th Avenue S., St. Petersburg, Florida 33711, U. S. A.
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Abstract

Aerial surveys (n= 88) were used to document locations and count sightings of manatees (Trichechus manatus latirostris) in the inshore waters of Tampa Bay, Florida, between November 1987 and May 1994. We made 5,358 sightings of manatees in 1,958 groups. Calves represented 8% of the manatees sighted. Counts were significantly higher in winter (= 79, n= 29 flights) than in non-winter (= 46, n= 47) months. Counts of manatees in winter increased significantly during the study, but warm-season counts did not. Regression models demonstrated a relationship between counts and environmental factors. Year-round counts were related to air temperatures and seasons, with highest counts in winter. However, in the winter season, counts were significantly correlated only with wind speed, not air temperature. Yearround counts were predicted to be curvilinear with highest counts at 15°C average air temperature. Areas used differed with season: in cold weather, 76% of all sightings occurred in zones with warm-water sources. High-use areas were identified for summer months. Spatial filter analysis was used to compare manatee density in high-use areas between two two-year time periods. The data indicate that (1) manatee use of Tampa Bay was high and increasing in winter, (2) there are particular zones of the bay where conservation of manatees and habitat should be a priority, and (3) sufficient information has been collected for management agencies to develop and implement manatee protection plans.

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