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Related Resources~
see New Scientist, Vol 151 No 2039, 20 July, 1996, page 22
The Florida Department of Environmental Protection and the Save the Manatee Club are also involved in protecting manatees. They help the manatee by adopting rules that regulate motorboat traffic, by protecting manatee habitat, and by developing public awareness and education programs about manatees. |
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West Indian Manatees, Trichechus manatus, are large, gray-brown aquatic mammals with paddle-shaped tails. There are less than 3000 West Indian manatees remaining in the United States. The herbivorous manatee have no natural enemies, though every year these gentle creatures suffer deaths from pneumonia, red tide and collisions with boats. A lesser known cause of manatee deaths involves water control locks and gates in Florida's inland waterways. These structures have crushed or drowned manatees that may be attracted to the flow of warm water and the accumulated vegetation near the structures.
According to Dr. Andrew Clark, the director of Engineering at Harbor Branch Oceanographic Institution in Fort Pierce, Florida, these gates become guillotines to manatees. In 1994 16 manatees deaths were attributed to water control structures.
In Florida hundreds of gates are required to control water levels in a vast network of canals. Mechanical gates, weirs and locks are used to regulate water levels. Tragically, manatee are sometimes caught in unattended or remotely controlled structures as they close, resulting in injury or death.
In an effort to eliminate or mitigate this form of manatee mortality, Harbor Branch has been working with the Army Corps of Engineers and the South Florida Water Management District.
There are two types of gates in use on the canals. Vertical lift gates are used for managing water levels for flood control and irrigation. These systems are controlled in response to a difference in water levels or controlled remotely from a control station. Lock gates, resembling huge swinging doors, are opened manually by a lock keeper, but it is still nearly impossible for the operator to see manatees in the murky waters.
Harbor Branch engineers have developed two different solutions, one for each type of structure. For the vertical lift gates, a sensitive polyurethane bumper was designed to detect light contact with a manatee. The touch-sensitive bumpers, coupled with a signal processor on the shore of the canal, is programmed to differentiate between floating debris and manatees. When the sensors detect a manatee the vertical lift gate stops closing, opens for a period and then tries again.
Photo courtesy of Army Corp of Engineers
More complex, the problem of detecting manatees between the swinging lock gates was also solved by the team of Harbor Branch engineers. These large gates swing independently in a wide arc, making it more difficult to detect a manatee between them. HBOI engineers designed a system using a series of acoustical beams, projected in a ladder-like pattern from one gate to another as they close. An interrupted signal, when three or more beams are broken simultaneously indicates the presence of a large object gates reopen.
Manatees have a difficult life coexisting with the human species. Technological advances like these detectors developed by the Engineering Division at Harbor Branch Oceanographic Institution may help to minimize man's impact on the environment and help to save the manatee, a species threatened by extinction.
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