Potential Adverse Impacts to Manatees

Manatee-clamshell    Blasting

Coastal development and activities such as dredge and fill projects, boat facility and boat ramp construction, bridge construction and even movie production can harm manatees or their habitat. FWC staff frequently provide expert opinion to state regulatory and planning agencies for potential adverse impacts to the Florida manatee. FWC provides recommendations for permit conditions or lease conditions to help reduce potential negative affects to manatees.

Direct impacts resulting from in-water work

In-water work in manatee habitat has the potential to directly injure or kill manatees depending on the type and location of work being proposed. The most common recommendations to offset these adverse impacts are known as standard manatee protection construction conditions Adobe PDF. These conditions (updated in 2011) were originally developed by the Army Corps of Engineers in 1979, when two manatees were killed during a dredging operation. These conditions represent the minimum amount of protection for manatees during in-water work. 
Additional conditions may be necessary, depending upon the project.  Examples of additional conditions that may be needed include, but are not limited to:

  1. The need for observers while work is being performed
  2. Seasonal restrictions (more manatees may be present during certain times of the year than during other times)
  3. Restrictions on the types of equipment
  4. Restrictions on the time of day work is being performed

Aerial photo of sea shore

Photo by Sea Shore Alliance


Boat Congestion

Projects that pose a significant threat to manatees may need an observer to watch for manatees while in-water work is taking place, or may need multiple observers to develop and use a Manatee Watch Program in order to sufficiently offset the potential adverse impacts. Examples include:

  1. Some types and locations of dredging projects
  2. Boat races or large boat parades
  3. Blasting projects - Blasting is sometimes used in bridge demolitions, dredging and movie productions that use explosives. Protected marine species blasting conditions, specific to the project, are recommended to offset these risks. These conditions typically include a Blast and Watch program, which includes an aerial survey with highly experienced observers. 

Entrapment risks in culverts and pipes

 Pipedrain-rescue   Manatee-drainpipe

Manatees sometimes enter submerged or partially submerged culverts and pipes, and occasionally become stuck. They have drowned and starved to death within these types of pipes. In response, we frequently recommend placing grates or other exclusion devices in front of the pipes to prevent manatee access.

Entrapment risks in storm water ponds and lakes

Being curious animals, manatees sometimes travel into areas that can get them into trouble.  In 2012, four manatees climbed over a weir in order to enter a large storm water treatment lake in Brevard County.  When the water receded, however, they became trapped in the lake, leaving them susceptible to cold weather.  An exclusion fence was installed to prevent future access to the lake.

 Manatee Climbing Over Weir 1 Manatee Climbing Over Weir 2  Manatee Climbing Over Weir 3 
 Manatee Climbing Over Weir 4  Manatee Climbing Over Weir 5  Manatee Climbing Over Weir 6

Take a look at this video if you would like to see how persistent manatees can be when they want to go somewhere: Manatee Hurdles Weir.

Crushing risks by large vessels

For large vessels that are greater than 100 feet long, have a vertically shaped side, (such as many of those found at Port or industrial facilities) and is moored along a vertical bulkhead, manatees may become entrapped and crushed between a ship and bulkhead. Fenders, buoys or cantilevered docks that provide a stand-off distance of four feet at maximum compression are usually recommended in order to avoid this type of death.


Wharf fender

Example of a wharf fender

Indirect (Secondary and Cumulative) Impacts to Manatees

Secondary and cumulative impacts to manatees, such as increased boat traffic as the result of the development of new marinas, are also reviewed by FWC staff. Commonly seen recommendations for boat facility development include permanent Manatee Educational Signs and Manatee Educational Programs. FWC approves where signs are installed and the number of signs at each location. Additional educational requirements or permit conditions may be necessary, depending upon the project. In some Florida counties, Manatee Protection Plans (MPPs) are developed, approved and used by the County, FWC, and the U.S. Fish and Wildlife Service.  These MPPs provide guidance that include recommendations addressing secondary and cumulative impacts from the development of new or expanding marinas. 

Habitat loss, such as loss of seagrass, occurs with coastal development. During our review, we attempt to eliminate or reduce losses to manatee foraging habitat.

Important Links

Standard manatee protection construction conditions (2011)

Manatee Protection Plans (MPPs)

Manatee Observer/Watch Program Information

Manatee Educational Signs

Grates or other exclusion devices for culverts and pipesAdobe PDF

DRAFT FWC Seagrass Survey Protocol Recommendations Adobe PDF

Permit Related Links

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