Underwater Collision

The manatees of Florida (Trichechus manatus latirostris) are much like the residents of Florida -- both like to subsist where it's warm. However, a large number of Floridians also enjoy boating and are fighting with the manatees for space in the temperate waters.

A January 9, 2003, synoptic (brief and comprehensive) survey by the Florida Fish and Wildlife Conservation Commission's (FWC) Florida Marine Research Institute (FMRI) counted a near-record number of manatees off the surrounding coasts of the state this year. About two times as many manatees were counted more than 3,000 -- since the count was first performed in 1991.

The synoptic survey achieves a head count of the animals by air and ground. In the winter, manatees congregate in certain warm water spots where they can be easily seen and counted in groups. In the summer, manatees spread along the southeastern coast of the United States from Louisiana to the Carolinas.

Boat propellers, the hull of boats, entanglement or ingestion of litter and fishing line all contribute to manatee deaths.

All aerial data are recorded on photocopies of navigation charts and entered into FMRI's marine resources geographic information system (GIS). GIS is a computer software system for making maps and doing analyses. The results are a primary source of data for management planning and decisions on the Florida manatee.

Challenging the Status

In 2001, the Coastal Conservation Association (CCA), an organization comprised of avid recreational fishers who have banded together to address conservation issues, petitioned FWC to re-evaluate the status of the Florida manatee. According to CCA, extensive data shows manatee populations have increased to a level of abundance that no longer fits the defined parameters for listing as an endangered species under FWC rules. Without a special permit, protection measures limit the waters boaters can sail and speed through.

A necropsy (autopsy) is performed on each deceased manatee found in Florida to pinpoint the cause of death. While the second-highest number of manatees were seen this year, FMRI has pointed out that the highest number of manatee deaths related to boat collisions also took place this year. Boat propellers, the hull of boats, entanglement or ingestion of litter and fishing line all contribute to manatee deaths. Other threats include flood gates/canal locks, cold stress and birth complications.

The December 2002 "Final Biological Status Review of the Florida Manatee," the most comprehensive scientific analysis of the Florida manatee to date, concluded the manatee could be downlisted to a threatened status, according to the state's criteria that apply to categorizing species as threatened. However, FWC has delayed the decision on whether to recommend downlisting of Florida manatees for 10 more months, claiming they want to accumulate and analyze more scientific data before the status is addressed. The Florida manatee was classified as endangered in 1973.

One aspect of the state listing criteria addresses projected or suspected future declines in the size of the statewide population of manatees. The state listing criteria specify one of the following benchmarks relative to population decline:

  • Endangered status -- A population reduction of at least 80 percent projected or suspected to be met within the next 10 years or three generations, whichever is longer.
  • Threatened status -- A population reduction of at least 50 percent projected or suspected to be met within the next 10 years or three generations.
  • Species of special concern -- A population reduction of at least 20 percent projected or suspected to be met within the next 10 years or three generations.

The population model used in the biological status review indicated it was possible that the manatee population in Florida could be reduced by 50 percent in the next 45 years (15 years per generation). Therefore, according to the state listing criteria, the manatee is most properly classified as threatened. Regardless of what the state decides, the manatee will remain on the federal endangered species list until it is determined that the species has "recovered" under federal criteria.

Examining Manatees

Research across the state is taking place to accurately assess manatees' population trends, evaluate the condition of their habitat and define ways to limit the amount of collisions manatees have with boats. Ultimately, such studies will contribute to the body of knowledge specific to the status of the Florida manatee.

Threats include flood gates/canal locks, cold stress and birth complications.

David Ceilley, a senior ecologist with the Conservancy of Southwest Florida said manatees are an indicator of ecosystem stability. "By protecting manatee habitat, we are protecting our own habitat and quality of life," Ceilley said.

Through environmental science research on south Florida ecosystems, the Conservancy is working to provide data and predictive responses of nature to human action.

Dr. Bruce Ackerman, a research scientist at the Florida Marine Research Institute, said, "We collect new data year-round on aerial survey counts, radio-tracking movement patterns, and cause of deaths from new carcasses found."

Currently, Ackerman is working on estimating manatee survival rates from photo-identification data from Tampa Bay and southwest Florida. Manatees have been studied photographically since 1983 in these areas.

Photographs of manatees' scars from collisions with boats make the mammals easier to distinguish. The analyses of survival rates are based on "sight-resight" estimates based on open population "mark-recapture" models. These complicated statistical programs estimate survival based on whether each individual adult manatee is seen at least once or missed during each winter.

Ackerman said the research institute would also be reanalyzing adult survival rates, using additional new photographs of manatees for identification. Current research may also lead to "Variations on the computer models used so far, possibly a different computer population model," Ackerman said.

A researcher at the University of South Florida recently finished work on developing and testing a detector that lights up when it hears sounds made by manatees. Dr. David Mann, an assistant professor in the College of Marine Science, explained that the device could warn boaters when a manatee is in the area.

The technology consists of a hydrophone that could be placed in the water, possibly on a buoy, and a computer system that recognizes sounds. When a manatee vocalization is heard by the hydrophone, a light on the buoy would go off to communicate to boaters that a manatee was in the area. This could warn boaters to be cautious of local manatees.

"By protecting manatee habitat, we are protecting our own habitat and quality of life," said David Ceilley, a senior ecologist with the Conservancy of Southwest Florida.

With the collaboration of two other investigators from Mote Marine Laboratory, Mann initially recorded manatee sounds. The sounds were analyzed and the parameters of the sounds were then measured. They found that the manatee noises were of a high frequency that could be successfully detected by a signal-processing device.

"Whether this would work with manatees and boaters depends on how much manatees vocalize and how boaters behave," Mann said. He also said manatees seem to vocalize when they are interacting with each other socially, but it's not certain how noisy they are when swimming solo. Boaters may choose not to respond to a signal from a detector or may disturb manatees if they are known to be nearby.

Regulate or Educate

Over the last three years, Dr. Richard Flamm has been researching the effectiveness of educating people in order to protect the manatee verses the effectiveness of regulations in place to protect the manatee.

By considering the perspective of a salesperson, Flamm said the project was formulated on the question, "How do you sell environmental stewardship?"

The first part of his three-phase study examined boaters' knowledge, attitudes and behavioral intentions regarding manatee protection and management in Florida. Greater knowledge about manatees was positively related with their conservation. Techniques to help educate people were identified through this initial phase.

Steps initiated in the second phase carried out several communication initiatives, such as having a local environmental stewardship organization, Tampa BayWatch Inc., disseminate information to boaters to influence their attitudes and beliefs about manatees.

In a December 2002 report, Flamm looked at whether the education materials distributed affected the intent of the boater. Monitoring of boating sites, as well as telephone-conducted surveys, helped provide the data for this research. This part of the study indicated that in order for behavior to change, people must develop a sense of empowerment. This goes beyond simply increasing people's knowledge of manatees, but to figure out how to encourage individuals to revisit the way they look at manatees. Right now, boaters may feel manatees are responsible for regulations that limit their freedom to boat where they want, as well as their speed.

"We found out the strategy is not the best. We need to rethink what we're doing," said Flamm concerning educational outreach.

In the final year of work on Flamm's extensive four-year project, he will re-evaluate previous studies and try to find the most successful technique to sell environmental stewardship.


The Conservancy of Southwest Florida -- www.conservancy.org

University of South Florida College of Marine Science -- www.marine.usf.edu

Florida Marine Research Institute -- www.floridamarine.org

Save the Manatee Club -- www.savethemanatee.org

Florida Fish and Wildlife Conservation Commission -- www.floridaconservation.org

If The Criteria Don't Fit...

By Patti Thompson,
Director of Science and Conservation
Save the Manatee Club

Special interest groups, like the marine industry, and organized boating and fishing groups claim that there are more manatees now than in 1991 when synoptic surveys were first conducted. However, scientific data presented at the Manatee Population and Ecology Workshop in April 2002 does not support the notion that there is an increase in the manatee population. A panel of population experts, manatee scientists and resource managers were unanimous in their agreement that synoptic surveys could not be used to assess manatee population trends.

Although the Florida Fish and Wildlife Conservation Commission (FWCC) adopted the listing criteria used by the World Conservation Union (IUCN) for classifying imperiled species, they conspicuously elected to downshift the definitions for these classifications. Under the state's modified language, in order for manatees to remain classified as endangered, they would have to meet the IUCN standards for critically endangered. Similarly, in order for manatees to be classified as threatened, they would have to meet the IUCN standards for endangered. Ironically, manatees would still be considered endangered anywhere else in the world but Florida due to Florida's irresponsible and arbitrary application of the IUCN criteria.

What may be most problematic is that manatees are stuck with extremely inflexible, one-size-fits-all-species listing/delisting criteria that do not consider individual species' life histories and are not suitable for long-lived, slow-reproducing animals, such as marine mammals. As a strong example of these misguided criteria, even the critically endangered northern right whale, whose population numbers approximately 300 animals, would not qualify as endangered or perhaps even threatened under the current FWCC definitions.

FWCC does not have scientific evidence to show that downlisting the manatee is warranted at this time. The state needs to develop appropriate listing/delisting criteria that fit the species before they can make that decision. Any assessment of the status of any species should be based on benchmarks similar to those supported by population experts at the Manatee Population and Ecology Workshop, including

  • Stable or increasing survival rates of all age classes;
  • Stable or increasing reproductive rates;
  • Comprehensive habitat protection; and
  • Significant reduction of human-related mortality.

Since the early 1990s, registrations for recreational vessels in Florida have increased by approximately 33 percent. Presently, there are more than 940,000 boats registered in Florida and approximately 400,000 boats registered in other states using Florida's waterways. With more and more boats on Florida's waterways, we can expect an increase in manatee injury and mortality.

This article originally appeared in the March 2003 issue of Environmental Protection, Vol. 14, No. 2, p. 71

This article originally appeared in the 03/01/2003 issue of Environmental Protection.

About the Author

Jim DiPeso is communications director at the Pacific Northwest Pollution Prevention Resource Center, Seattle.

Featured Webinar