Red tide played a big role in manatee deaths this year, but boat strikes remain constant threat

A manatee and her calf rise for air while swimming in Ware’s Creek in Bradenton in 2016.
A manatee and her calf rise for air while swimming in Ware’s Creek in Bradenton in 2016. Herald file photo

A prolonged red tide season that bled over from 2016 played a large role in deaths of the Florida manatee this year.

Red tide’s presence was visible — visually and nasally — from September 2016 through February in Manatee County, with other areas along Southwest Florida also being exposed.

Also known as the accumulation of the phytoplankton Karenia brevis, red tide used to be a one-off reason for manatee mortality, said Katie Tripp, Save the Manatee’s director of science and conservation.

“It’s not even unusual anymore,” she said.

In 2016, a total of 520 manatees were reported dead statewide, with various causes such as boat strikes, cold stress syndrome or natural. This year, preliminary counts through Dec. 15 put the count at 513. Many of them occurred in Brevard or Lee counties, as a lot of manatees congregate in those waters. More often than not, the cause of death goes undetermined.

Between 2013 and 2014, statewide recorded deaths had significantly dropped from 830 to 371. Since then, the figures have steadily grown. But FWC veterinarian Martine Dewit said those totals shouldn’t be the focus, as it’s likely it doesn’t represent all manatees that have died each year. Instead, she hones in on the causes.

The toxic red tide blooms accounted for at least 73 deaths in all of 2016 and an estimated 63 deaths through August of this year. The highest recorded by FWC since 1996 was four years ago, with 277 deaths where red tide either tested positive or was suspected.

While red tide was a significant event, there’s one thing that has been a constant: boat strikes. That and lack of warm water are the biggest threats to manatees, she said. In Manatee County, boat strikes accounted for about 25 percent of the deaths recorded in 2016. Even one of South Florida Museum’s rehabilitating manatees, Lagoona, is recovering from being hit.

Last year set a record for boat strikes, which were responsible for killing 106 manatees. So far in 2017, there have been an estimated 101 deaths associated with watercraft hits.

Tripp wonders if there will be another record.

In the new year, she hopes to discover how many of these deaths were by accident or boater error. If boaters strike a manatee, Tripp said, submitting information on how fast they were going and what type of boat they used could help answer this.

While the focus used to be about numbers, more creative solutions are needed to make sure the water is safely shared as manatee populations rebound.

“If it’s something that’s preventable, you want to do what you can to prevent it,” she said.

Sick, injured or dead manatees should be reported to the FWC Wildlife Hotline by calling 1-888-404-3922.

Hannah Morse: 941-745-7055, @mannahhorse