Manatees in Sebastian, Florida

Manatees are mainly a warm-season presence at Sebastian: Florida State Parks says they inhabit the waters around Sebastian Inlet State Park from March to October.

Water temperature sets that calendar. Indian River County's lagoon program says manatees reach about 1,000 pounds on average yet carry very little body fat, and they cannot survive in water colder than 68 F (Indian River County). The county adds that manatees can travel as far as New England in summer but must return to warmer Florida water for winter, and that most of the Atlantic population uses the Indian River Lagoon either to reach warm-water sites, such as springs, thermal basins and power plant discharges, or to move between summer and winter habitat.

The FWC uses the same 68 F line to time its winter counts. Its synoptic survey is flown only when water near most major aggregation sites is below 68 F, the conditions in which manatees gather at warm refuges instead of spreading through the Indian River Lagoon off Sebastian (FWC synoptic surveys).

Spring is when the animals spread back out. In March 2020 the FWC reminded boaters that at that time of year manatees leave their winter refuges and are more likely to be found in rivers, canals and nearshore waters, a reminder Sebastian Daily ran for Sebastian Inlet area readers (Sebastian Daily).

One former winter refuge lies south of Sebastian in Vero Beach. Sebastian Daily reported on January 29, 2026 that the canal near the Vero Beach power plant was once known for drawing manatees to its warm water discharge (Sebastian Daily).

Around Sebastian, manatees are documented in the Indian River Lagoon waters of Pelican Island National Wildlife Refuge, at the Bayside Marina docks in Sebastian Inlet State Park and in Sebastian Inlet itself.

Pelican Island National Wildlife Refuge, near the Atlantic coastal community of Sebastian, covers more than 5,400 acres of protected waters and lands (U.S. Fish and Wildlife Service). The refuge's About Us page says the Indian River Lagoon runs 156 miles down Florida's east coast and lists the Florida manatee among its federally protected species, with the green sea turtle and the wood stork.

On the barrier island, Florida State Parks names the marina docks at Bayside Marina in Sebastian Inlet State Park as a location for bird, manatee and dolphin viewing year round, and says Atlantic bottlenose dolphins are commonly seen in the water around the park (Florida State Parks). The year-round note and the March to October note sit on the same park page; the second describes when the animals are usually present.

The Sebastian Inlet District keeps a photo record of the inlet's marine life on its wildlife sanctuary page, and manatees (Trichechus manatus latirostris) appear there alongside Johnson's seagrass and mixed seagrass beds from the flood shoal inside Sebastian Inlet.

Seagrass is the reason those shallows matter. Indian River County says the lagoon holds seven species of seagrass, with shoal grass and manatee grass the dominant species in Indian River County, and that manatees are herbivores that eat only plants and stay in shallow water near their food (Indian River County).

No count exists for Sebastian alone, but the FWC's most recent abundance survey estimated 3,940 to 6,980 manatees on Florida's east coast, which includes Sebastian, and 8,350 to 11,730 statewide for 2021 to 2022.

The east coast flights for that third statewide survey ran from November 30 to December 6, 2022, over the Atlantic side that includes Indian River County (FWC abundance estimate). The FWC presents each result as a 95 percent credible interval rather than a single number because some manatees are submerged or missed by observers. The agency's species page uses the low end, saying the population has grown to a minimum of 8,350 animals, and notes that the species was reclassified from endangered to threatened under the federal Endangered Species Act in May 2017 (FWC Manatee Program).

Older winter synoptic counts tally manatees at warm-water sites and give a minimum, not a population size. The FWC conducted them 33 times from 1991 through 2019, last in 2019, and says the counts swing with weather and are not suitable for long-term trends, so the figures below for the coast that includes Sebastian are best read as snapshots (FWC).

Manatees from the Indian River Lagoon off Sebastian starved in an Unusual Mortality Event that ran from December 1, 2020 to April 30, 2022, when 1,255 manatee carcasses were documented on Florida's Atlantic coast.

The FWC and the U.S. Fish and Wildlife Service concluded that starvation due to lack of forage in the Indian River Lagoon caused the deaths, after the lagoon lost much of its seagrass (FWC). Cold made it worse: 1,039 of the 1,255 deaths came during the winters of 2020 to 2021 and 2021 to 2022, and partners carried out 137 rescues along the coast.

The agencies also tried feeding. During the winters of 2021 to 2022 and 2022 to 2023, staff and volunteers supplied at least 600,000 pounds of leafy greens at a supplemental feeding site in the lagoon region hit hardest by seagrass loss, the same Indian River Lagoon system that borders Sebastian.

The event is formally over. The last death from starvation linked to a lack of forage was documented in March 2023, and the U.S. Fish and Wildlife Service declared the event closed in a letter dated March 14, 2025 (FWC). The FWC credits slow seagrass recovery in some key areas, including parts of Mosquito Lagoon at the northern end of the Indian River Lagoon, while saying conditions in portions of the lagoon remain a concern. Researchers have since observed mating herds and cow and calf pairs on the Atlantic coast.

The threats that remain near Sebastian are human ones. The FWC names coastal development and watercraft collisions, and Indian River County lists watercraft strikes, entanglement in fishing gear and the loss of warm-water habitat and feeding areas in the lagoon (Indian River County).

Manatees in Sebastian waters fall under the Florida Manatee Sanctuary Act, the federal Marine Mammal Protection Act and the Endangered Species Act, and Indian River County has had an approved Manatee Protection Plan since 2004.

State protection is old. The FWC says Florida manatees were first protected through Florida state law in 1893, and that today the Sanctuary Act, section 379.2431(2) of the Florida Statutes, covers them in state waters such as the Indian River Lagoon and the St. Sebastian River (FWC).

Indian River County was identified as one of 13 key Florida counties to develop a manatee protection plan, prepared with the FWC and the U.S. Fish and Wildlife Service. Federal, state and local governments use the plan when reviewing permit applications in Indian River County (Indian River County). The county's guidance for anyone on the lagoon is to observe from a safe distance and not approach, touch, feed, water, chase or harass manatees, and inside Sebastian Inlet State Park divers must keep a minimum distance of 50 feet from manatees at all times (Florida State Parks).

Boat speed zones are the other layer, and they are under review. Sebastian Daily reported on January 29, 2026 that the Indian River County zones were last revised in 2002 and that the FWC proposed changing the idle speed zone near Sebastian Inlet to a slow speed zone, with current restrictions staying in place until final rulemaking (Sebastian Daily). The zone boundaries themselves are covered on the Digital Towns page on Sebastian manatee protection zones.

Injured, distressed or dead manatees anywhere from the St. Sebastian River to Sebastian Inlet are reported to the FWC at 888-404-3922, or by dialing #FWC or *FWC from a cell phone (FWC).