A deadly trend: Boats top all causes of manatee deaths in 2019

120 manatees killed by boats so far this year

As more sea cows and captains crossed paths on Florida’s waters, boats became the leading cause of manatee deaths this year and are on course to top last year’s record 124 manatee deaths by boat, according to early state statistics.

News 6 partner Florida Today reports that through Nov. 22, Florida had 120 manatee deaths by boat, topping the five-year average of 91 boat-related manatee deaths through that same point of the year, data from the Florida Fish and Wildlife Conservation Commission show.

Last year, natural causes were the leading cause of death, claiming 230 manatees, 79 of them in Lee County, FWC statistics show.

Here is FWC’s manatee mortality data for 2019, through Nov. 15, the most recent available. Drag your mouse over the bar graph to see how many manatees died from each cause.

Overall, sea cows fared better through mid November this year than in the last few years, with 465 dying from all causes by Nov. 22, compared to 760 manatee deaths by that date in 2018 and 483 manatee deaths by that date in 2017.

A record 830 manatees died in 2013, including 158 of 244 manatees deaths that year in Brevard from undetermined causes. Biologists suspect many of those 158 manatees may have fallen victim to a seagrass die-off that disrupted the makeup of healthy bacteria in their digestive tract, leading to the disease.

The second most on record — 824 manatees — died last year.

Boating advocates who fight against manatee go-slow zones have long pointed out that manatee deaths are going up mostly because the species' population growth. Brevard and Lee counties, in particular, tend to have the most manatee deaths from all causes because they have large manatee populations lured there by vast seagrass habitats.

This year's been no exception. Lee County's 24 boat-related manatee deaths were the most in Florida, followed by Brevard's 13 watercraft-related deaths. Volusia ranks third with 12 watercraft-related manatee deaths.

“It is above the 5-year average and getting close to last year’s record number of 124 cases documented,” Martine deWit, an FWC veterinarian, said of this year’s boat-related manatee deaths in Florida. “Most of these mortalities happened in the first half of the year. Extra alerts went out at that time, and at least these cases were not coming in as frequent the second part of 2019. Hotspots are the Indian River Lagoon and Lee county.”

Again, boaters point to more manatees as the reason.

“Even though we continue to focus on mortality and watercraft, the real issue might be that the (manatee) population has shown a consistent 5% annual growth rate over the last four decades, doubling every 10-15 yrs and is nearing 10,000,” Bob Atkins, president of Citizens for Florida’s Waterways, a boating advocacy group in Brevard, said via email. “How long can the habitat, especially the seagrasses, sustain this level of explosive growth.”

Florida’s annual manatee counts have more than doubled in the past 20 years, to a record 6,620 animals in 2017, according to statewide yearly aerial and ground counts. As a result, the federal government reclassified the manatee from an endangered to a threatened species, a less serious designation under the federal Endangered Species Act.

Florida wildlife officials counted 5,733 manatees this year during its annual winter survey, Jan. 28 to Feb. 2. But biologists consider the statewide annual surveys only a minimum count of the manatee population, so there could be thousands more sea cows.

Meanwhile, registered vessels have increased as well, although they yet to recover to more than 1 million vessels in Florida from before the 2008 economic crash.

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