Researchers from Harbor Branch Oceanographic Institute at Florida Atlantic University recently developed and improved upon a unique acoustic system that may help save manatees from being injured or killed in flood gates or boat locks. (Photo credits: top, Save the Manatee Club; right, Joe Querry, ACOE)

Researchers from Harbor Branch Oceanographic Institute at Florida Atlantic University have recently developed and improved upon a unique acoustic system that may help save endangered manatees from being injured or killed in flood gates or boat locks.

The “Manatee Acoustic Detection Sensor Protection System” is composed of acoustic transmitters and receivers that detect manatees as they pass through the gates of a lock. When a manatee blocks the acoustic beams (which the manatee cannot hear), the gates stop and remain open long enough to allow the manatee to pass through safely.

Manatees are native to Florida and were using its waterways long before there were navigation locks, but since the construction of Florida’s navigation lock structures, they have had to learn to negotiate them. For example, manatees appear to be aware of scheduled openings and closings of locks and will often show up prior to that time. Once at the gates, they will linger there, waiting for them to open.

A sensor is activated by blocking the path between the transmitter and receiver. The gates will automatically stop and allow the manatee to pass unharmed. (Graphic courtesy Harbor Branch Oceanographic Institute at Florida Atlantic University)

But navigation lock and flood control structures have always presented a problem for manatees. In fact, entrapment in water control structures and navigational locks is the second largest identified cause of human-related manatee deaths after watercraft collisions. Manatees can be crushed in closing flood gates and canal locks that are used to protect against salt water intrusion and flooding. This problem is particularly acute in south Florida where there are many water control structures. Manatee deaths from drowning have also occurred when the tremendous suction that is created by water rushing through opening gates pins animals under the water. Since 1974, at least 192 manatees have been crushed or drowned in these structures.

“We installed the prototype acoustic system about 10 years ago in the St. Lucie lock, “ said Larry Taylor, project manager for manatee protection systems at Harbor Branch. “Since then, we have redesigned the system with underwater sensor cartridges. The device is now smaller, cheaper, faster and easier to operate.”

Harbor Branch recently received a $5.8 million federal contract from the U.S. Army Corps of Engineers (ACOE) to install the acoustic system in southern Florida on six navigation locks around Lake Okeechobee. Among these are Moore Haven lock at Clewiston and the Port Mayaca lock where the St. Lucie River meets Lake Okeechobee, a waterway that links the Atlantic Ocean to the Gulf of Mexico.

"Manatees must deal with a high number of mortalities from human-related causes," said Patrick M. Rose, Executive Director for Save the Manatee Club. "The acoustic system will hopefully prevent many injuries or deaths in these man-made structures and provides another level of protection as manatees travel along Florida's waterways. Special thanks to the Harbor Branch staff for their ingenuity and effort in developing this system and to the ACOE for the funding they have put into this project."

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