| (Reprinted from the Endangered Species Bulletin * Vol. XXI No. 3)
Die-off Decimates Florida Manatee Since January 1, 1996, more than 260 Florida manatees (Trichechus manatus), or about 10 percent of the known manatee population in the United States, have been found dead. Some 157 of these deaths occurred in southwest Florida since March 5, 1996. Recent analyses of blood and tissues are providing clues to this die-off but so far have failed to determine conclusively the cause. Numerous Federal, State, and private agencies and organizations have been assisting Florida Marine Research Institute scientists with the ongoing investigation by testing the hypotheses most likely to explain the record-breaking number of manatee deaths. Efforts have focused on three possible factors: 1) a biological toxin, such as that produced by the dinoflagellates that cause a "red tide," 2) a disease caused by a virus or bacterium, or 3) a contaminant substance, such as a pesticide. It is also possible that a combination of factors was involved. Tissue samples collected from dead manatees have been sent to laboratories across the country with expertise in identifying biotoxins, infectious agents, and contaminants. As of early May, none of the results were conclusive. Note sidebar. Live manatees exhibiting neuromuscular problems consistent with those previously described in manatees exposed to red tides have been rescued in southwestern Florida and taken to a rehabilitation facility at Lowry Park Zoo in Tampa. The recovery of three females took several days, during which they required assistance to stay afloat for breathing. A male manatee rescued recently by State biologists is expected to recover. Scientists are hopeful that the die-off is over. As of May 10, no fresh manatee carcasses had been found since April 25, 1996. The U.S. Fish and Wildlife Service and National Biological Service will continue to assist Florida Marine Research Institute researchers in their efforts to document and understand this tragic manatee die-off, and will identify research and management needs to prevent or reduce such events in the future. Robert Turner, the FWS Manatee Coordinator, is located in the Jacksonville, Florida, Field Office. Sidebar: The Florida Marine Research Institute has organized an effective team approach to document this record high mortality. Biologists collected information on dates and locations of dead manatees, and gathered environmental data on water temperatures, salinity, and counts of red tide organisms. The information has been entered into a geographic database so that clues to the manatee deaths can be identified and analyzed. A preliminary review has shown a clear correlation between the distribution of dead manatees and sites with high red tide counts, but a definitive causal relationship between the red tide and the manatee deaths has yet to be firmly established.
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