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Lee County had second highest manatee deaths in 2021; FGCU prof: stopping pollution would help

File photo
The Florida Fish and Wildlife Conservation Commission reported about 1,100 manatees died last year after by being cut open by spinning boat propellers and crushed in closing flood gates and canal locks. Many also died from starvation as polluted marine shallows aren't allowing enough sea grass to grow to feed the popular threatened species

The news was not good for Florida's manatee population on Tuesday.

The Florida Fish and Wildlife Conservation Commission released preliminary numbers showing 1,100 of the sea cows perished in the state with causes including boat strikes, cold stress, injuries from flood gates and canal locks, as well as from natural causes.

Lee County recorded the second highest number of those deaths in 2021 with 110. Brevard County was first, marking the most such deaths at 358.

That 2021 deaths figure was a huge increase over annual numbers from the past five years. In that time span only 2018 came close with 824 manatee deaths. The other years ranged from 520 in 2016 to 637 in 2020.

Dr. James Douglass, an association professor of marine and earth science at FGCU, said those deaths don't bode well for the state's manatees.

"Well, the total manatee population in the state is less than about 7,000. And so when you're talking about 1,000 deaths, that is a huge chunk of the population," Douglass said. "So, it's not only that it's a big number, but it's a big number subtracted from the total population, which is not that much bigger. So, it's really devastating to the manatees that died, but it's also a big threat to the sustainability of the manatee population in Florida into the future. If we keep getting numbers like that dying every year, it's not going to be but a few more years before there's no manatees in Florida."

Still, Douglass said, there are things that could be done.

"We know that a lot of the manatees are dying because of factors that are linked to starvation. There's not enough seagrass for them, and a main reason for that is water pollution. So this (is) sort of a chain reaction where pollution causes algae blooms, algae blooms cause the seagrass to die, and then the manatees die because there's not enough seagrass," he said.

Douglass said stopping that chain reaction means stopping the pollution.

"One of the things that it does is it darkens the water. That's why the seagrass is dying ... and then that leads to the manatees dying," he said. "So, you know, anytime you see murky water with no seagrass in it, that's means there's no food for manatees in that area. And that's something to be concerned about."

Lee County's overall death toll in 2021 included eight by watercraft, 23 perinatal, 16 natural, five undetermined and 56 that were not necropsied.

TO REPORT A SICK, INJURED, DEAD, OR TAGGED MANATEE: Call FWC's Wildlife Alert Toll-Free Number: 1-888-404-FWCC (1-888-404-3922), press "7" to speak with an operator. Cellular phone customers: *FWC or #FWC

Lee's 2021 manatee deaths were highest in February when 23 of the large aquatic mammals perished. Of those, 14 were not necropsied, five were natural, 2 from boat strikes and 2 from perinatal causes.

Other Southwest Florida counties reporting manatee deaths included Charlotte with 25, Sarasota with 19, and Collier with 8.

Braun, Michael
File photo/FWC
Special to WGCU
Wildlife experts with the FWC perform a necropsy on a manatee carcass.

Explanation of death categories are as follows:

  • Watercraft: Watercraft-related mortality. Death may result from propeller wounds, impact, crushing, or any combination of the three.
  • Crushed/Drowned in Flood Gate or Canal Lock: Manatees killed by crushing or asphyxiation in flood gates and canal locks.
  • Other Human-Related: Manatee deaths caused by vandalism, poaching, entrapment in pipes and culverts, complications due to entanglement in ropes, lines, and nets, or ingestion of fishing gear or debris.
  • Perinatal: Manatees less than or equal to 150 cm (5 feet) in total length which were not determined to have died due to human-related causes.
  • Cold Stress: Manatees which die as a result of exposure to acute or prolonged cold weather. Animals are usually emaciated and in a general state of malnutrition. (Combined with "Other Natural" in some printouts.
  • Other Natural: Manatee deaths resulting from infectious and non-infectious diseases, birth complications, natural accidents, and natural catastrophes (such as red tide blooms).
  • Undetermined; Too Decomposed: Manatee deaths in which the cause of death could not be determined due to an advanced stage of decomposition.
  • Undetermined; Other: Manatee deaths in which the carcass was in good condition (fresh or moderately decomposed), but necropsy findings were inconclusive. (Combined with "Undetermined" in some printouts.)
  • Verified/Not Necropsied: Manatee deaths that were reported and verified, but a complete necropsy was not performed (Combined with "Undetermined" in some printouts.) Some manatees will still receive varying levels of examination and tissue collection.

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