Eight hundred Florida manatees died in 2022, according to the Florida Fish and Wildlife Conservation Commission. While this is an improvement over the 1,100 manatee deaths in 2021, it’s higher than the five year average of 741.
Brevard County had the most manatee deaths with 346. Lee County was second in manatee deaths at 82,
There were fewer deaths due to water craft collisions in 2022, with 76 deaths. The five year average is 113 manatee deaths per year due to watercraft collisions.
In 2022, 19 manatee deaths were due to injuries in flood gates or locks. That’s more than triple the five year average of 6 deaths related to flood gates or locks.
As in 2021, most of the manatee deaths in 2022 were apparently connected to starvation. This has been a recurring problem in the Indian River Lagoon, where algal blooms known as “brown tide” shades out the sea grass, a main food source for the manatees.
According to the FWC report, “Mortality was high due to the ongoing Unusual Mortality Event (UME) from starvation and malnutrition on the Atlantic coast.
“Cool temperatures have a negative effect on manatees compromised by malnutrition, causing this UME to spike during winter. It is possible that a relatively warm December 2021 and less cold days in winter 2021-2022 contributed to lower mortality from starvation in early 2022. The number could also be lower if the population size decreased, after the unprecedented mortality in 2021 left less manatees to die on the Atlantic coast. Another uncertainty is carcass detection, if there is different distribution of animals between years, less carcasses may be noted when these occur in remote areas,” the report explains.
The increase in deaths in flood control gates or locks could be due to manatees moving into areas they had not previously used, the report states.
“Researchers documented 19 (preliminary number) manatee carcasses that were crushed, impinged, or drowned in water control structures and navigational locks. This is the highest yearly number on record since the start of the manatee mortality database in 1974. The FWC performs a detailed investigation into every mortality reported near a structure. The 2022 mortalities occurred at nine different structures. Over the years, manatee protection measures and retrofitting these structures with protection devices have resulted in safer passage, but most of this year’s mortalities occurred at structures without manatee protection. It is possible that changes in manatee distribution now cause higher traffic through structures and locks that previously did not encounter many animals. Flooding can also change operation of water control structures. FWC and U.S. Fish and Wildlife continue to work closely with structure managers to address and reduce such deaths. At least eleven live manatees were successfully rescued and released from entrapment by water control structures,” the report states.
None of the deaths were connected with Hurricane Ian or Hurricane Nicole, according to the report. There was no increase in deaths following the storms. FWC staff and partners successfully rescued five manatees that had been trapped in retention ponds or other areas after flood waters receded.
For the counties around Lake Okeechobee:
• Okeechobee County had two manatee deaths. One was due to a flood gate/lock accident. The cause of other manatee death was undetermined.
• Glades County had six manatee deaths due to flood gate/lock accidents and two deaths with undetermined causes.
• There were no reported manatee deaths in Hendry County.
• Palm Beach County had a total of 13 manatee deaths: one due to human interaction; eight due to natural causes; and four from undetermined causes.
• Martin County had 14 manatee deaths: two due to watercraft collisions; two due to other human interaction; one due to cold stress; six from natural causes; and three from undetermined causes.
A petition filed in November with the U.S. Fish and Wildlife Service maintains it was an error to take manatees off the Endangered Species List in 2017. Manatees are now listed as “threatened.”
According to the petition, filed by the Center for Biological Diversity, Harvard Law School Animal Law & Policy Clinic, Save the Manatee Club, Miami Waterkeeper and Frank S. Gonzalez Garcia, “The populations of both subspecies of manatees are decreasing. From its peak in 2017 until 2019, the Florida manatee’s observed population decreased by an average of 6.94% annually. A subsequent unusual mortality event on the Atlantic coast has driven greater population decline, and more than 1,100 Florida manatees died in 2021 alone, representing over 13% of the subspecies’ estimated population.”
The petition states many manatee deaths are due to the loss of seagrass. In the Indian River Lagoon, excessive nutrient pollution has caused algal blooms which prevent sunlight from reaching the seagrass. Causes of sea grass loss include boating, coastal development, dredging, stormwater runoff, septic tanks, legacy nutrients and fertilizers.
In addition, the manatees are losing access to natural springs which maintain a constant temperature year round and historically provided the mammals with cold weather refuges. Consumptive withdrawal of groundwater has reduced the flow rates of the natural springs, the petition maintains, and threatens their sustainability as manatee habitats.