More Florida manatees have been crushed by flood gates, contributing to a deadly year

Florida's manatees had an especially deadly year in 2020, marked by particularly grim incidents: flood gates closing and crushing the "gentle giants," and even decapitating one.

Manatee deaths are common as their population increases, but the majority are caused by being struck by boats and cold-water stress.

It's far more rare for manatees to be crushed by one of the state's countless flood-control structures, most of which have sensors that prevent them from closing on a nearby manatee.

Out of 637 manatees killed in Florida last year, 11 were crushed or drowned by flood gates, according to a preliminary report from the Florida Fish and Wildlife Conservation Commission.

"That seems wholly preventable," said Jaclyn Lopez, Florida director of the Center for Biological Diversity. "We just have to be doing a better job to address these low-hanging issues."

Overall, there were 30 more manatee deaths in 2020 compared to 2019.

Of the deaths last year, 90 were caused by boats and 52 by cold stress, the state report said.

The 11 deaths caused by flood gates came as a surprise to Pat Quinn, Broward County's manatee manager.

"I can't remember the last time we might have had a flood gate kill a manatee," he said. "In my 14 years, maybe this happened once or so. It's really not a problem we have down here."

Rachel Silverstein, executive director of the non-profit preservation group Miami Waterkeeper, said most flood control structures have sensors that detect nearby manatees.

"The salinity control structures opening and closing used to be one of the largest causes of death of manatees in Florida," she said.

But the state said some of the structures involved in manatee deaths in 2020 were not equipped with the sensors.

In one December death near Miami's Little River, a manatee was decapitated by doors on a salinity control lock. Lopez said the deaths by the flood control structures are particularly disturbing.

"Manatees will get out of the way if they can, if they have enough time and enough space," she said. "But getting decapitated or crushed or injured by a lock mechanism seems like a wholly preventable type of fatality."

Despite a record number of boating-related deaths in 2018, the state's manatee population is healthy, including locally. Florida is believed to have more than 8,000 manatees statewide, according to the FWC. Awareness programs and efforts by the FWC and other groups have generally reduced deadly accidents.

Broward and Miami-Dade counties have fewer manatees, as it is believed that food supplies such as sea grass keep manatees farther north, around Palm Beach County. Two exceptions in Broward draw more of the sea cows, which congregate in warm waters discharged from the Florida Power & Light's cooling canals to the east and west of Fort Lauderdale International Airport.

The FWC said COVID-19 concerns early last year prevented it from conducting necropsies on many carcasses. There were 212 manatees that didn't get necropsies in 2019, almost twice as many as each of the previous two years. But it said necropsies were conducted as usual in the last half of the year.

Lopez said she expects as the manatee population grows, manatee mortality will grow accordingly. But she warned we must still be sensitive to things that threaten manatees such as boats, harmful algal blooms such as red tide or blue-green algae, or loss of sea grass.

"Those are things if we don't get a handle on, yeah, we might see more manatees in the short term," she said, "but we have the potential to have a catastrophic collapse as well."

The traditional manatee season in Florida runs through March 31.