Fact: Many researchers agree that in two areas in the state of Florida the manatee population is growing, through both reproduction and migration of manatees from other areas of the state. These two areas, Blue Spring in Volusia

County (known by researchers as the Upper St. Johns River) and Crystal River/Kings Bay in Citrus County (known as the northwest region), have been protected areas for over 30 years and are relatively rural areas with less boat traffic. Blue Spring is a no-entry zone (refuge) and several no-entry zones (sanctuaries) have been established in Kings Bay.  Both sites also have substantial slow speed zones in surrounding waterways.  It is believed that, because of these factors, these two sub-populations have increased.  It is important to note, however, that these two groups combined comprise only about 16% of Florida's total manatee population. (1)

 

No one yet knows the status of the two remaining manatee regional sub-populations.  The data available from these regions is not sufficient to make a statistically reliable estimate of the population trend.  The East Coast and Southwest manatee populations may be stable at best or may be declining. This is important because these two regional sub-populations make up the remaining 84% (the vast majority) of the manatee population in Florida. (1) 

 

Fact:  More manatees were counted than ever before (3,276) during the synoptic survey conducted in January 2001. That is very good news. Most researchers have always believed the manatee population was somewhere between 2,000 and 3,000 animals.  While it is tempting to try to make a correlation between the higher counts and increases in the population, it is important to note that synoptic survey counts do not provide statistical estimates of population size and thus are not used to determine trends in the population.  Rather, these surveys provide a minimum count at a particular point in time.  Looking at all of the synoptic survey results, it is evident that there is a tremendous amount of variability among the survey results.  The outcome of the survey is highly dependant on weather conditions, and weather conditions will not be optimal in all areas of the state at the same time.  Factors such as wind, glare, water clarity (turbidity), and the cold front's length and severity all affect the researchers' ability to see and count manatees. (2)     

 

In addition, there are other factors, aside from minimum population counts, that determine when manatees can be downlisted or delisted. These factors include whether the threats to their habitat are stable or declining and whether the number of manatees dying each year is stable or decreasing. The criteria for determining habitat stability have not yet been determined and there has been an alarming upward trend in mortality from boat collisions and other causes in the past decade. (3)

 

Fact: The higher manatee count from the last synoptic survey gives us some breathing room but that is all.  No one knows how many manatees are enough to maintain a healthy, genetically viable population (minimum viable population number).  Of particular concern is the increasing number of watercraft-related manatee mortalities.  Watercraft-related manatee mortality is the leading cause of death of adult manatees.  Large mammals like the manatee, which have a long potential life span and slow reproductive rate, normally have a low adult mortality rate.   Manatee population viability analysis and population modeling completed by Marmontel (1993) indicated that even a small increase in adult mortality increased the probability of extinction.   (4, 5)

 

It is also important to note that the threats to the long-term survival of manatees are increasing.  There are more and more boats using manatee habitat, increasing the risk of dangerous collisions for manatees.  Increasing coastal development leaves fewer quiet, pristine areas where manatees can rest, feed, breed, give birth, and rear their young without disturbance.  In addition, increased shoreline development also results in more stormwater runoff, which increases water pollution and turbidity levels, in turn threatening habitat features such as seagrass, a manatee food source.

 

Fact: No one knows how many manatees there were in the 1950s and 1960s because there was little or no research being done (3). There could have been 10,000 manatees in Florida at that time or 500. Scientific, methodical research to determine the minimum population statewide began in earnest in the early 1990s when the first synoptic aerial surveys were conducted. Each synoptic survey results in a minimum population number.  However, because of extreme variability between surveys due largely to weather conditions, this does not yield a statistical estimate of the population and cannot be used for population trend analysis.  (2)

 

Fact:  There have been 4,042 manatee mortalities documented in Florida from 1974--2000.  Of those, 988 were attributed to watercraft collisions, 168 were attributed to flood gates or canal locks, 108 were other human-related, 852 were perinatal (dependent calf), 143 were natural cold stress, and 532 were other natural.  For the remaining 1251 carcasses no cause of death was identified: in the majority of cases (704) the carcass was too decomposed to determine a cause of death.   The perinatal/dependent calf category is also not a cause of death, rather it identifies that the manatee died around the time of birth, the manatee was less than 150 cm (5 ft.) In total length and was determined to have not died due to human-related causes.(6) 

 

Any species of animal living in the wild will suffer losses from natural causes and can usually overcome those losses. But the manatee population must also deal with a high number of additional mortalities caused by human-related factors. Because human-related manatee deaths are preventable, this area is the most logical place to begin in order to reduce mortalities. 

 

Watercraft-related manatee mortality is the leading identified cause of manatee death in Florida.  Most concerning is the fact that watercraft collisions is the leading cause of death of adult, reproductive age, manatees.  Large mammals like the manatee, which have a long potential life span and slow reproductive rate, normally have a low adult mortality rate.  Losing reproductive adult female manatees can be doubly lethal if they are pregnant or have a dependent calf. 

Further cause for concern comes from recent research conducted at the Florida Marine Research Institute, which revealed that of the manatees whose carcasses had been recovered in the salvage program, few were living past the age of 30 and the majority of animals died between the age of 0 and 10 years, nowhere near their estimated life expectancy of 60 years.(7, 8)

 

Reducing adult manatee mortality is the most effective method to increasing the manatee's recovery rate, and the reduction of watercraft-related mortality is the most productive and reliable means to reduce adult manatee mortality.   Other causes of manatee mortality do not affect the adult age class in numbers as large or significant as watercraft mortality.   Manatee population viability analysis and population modeling completed by Marmontel (1993) indicated that even a small increase in adult mortality increased the probability of extinction (4, 5). 

MYTH #6: There isn't enough habitat to support more manatees.

 

Fact: Florida has over 8,400 miles of tidal waters, 11,000 miles of rivers and streams, and 10,000 miles of canals.  Many of these waters are used by manatees.  Manatees feed on a wide variety of vegetation including floating, submerged and shoreline vegetation.   There is no scientific evidence that manatees are nearing the carrying capacity of the available habitat. 

However, much of prime manatee habitat either has been destroyed or is being degraded by the fast pace of development. This is the reason it is crucial to protect enough habitat to support a viable manatee population. One way to protect habitat is to adopt additional sanctuaries and refuges that either limit or prohibit human activities in essential manatee habitat areas.  Another way is to establish coastal development guidelines or plans that direct development away from ecologically sensitive areas and/or habitat areas that provide for the manatees' biological needs.

 

Fact: There would be 100% access by boat to shoreline property by property owners and their guests but not by the general boating public. In addition to protecting manatees in essential habitat, this limitation on boat traffic would help protect both natural shorelines and seawalls from erosion and allow for more backyard privacy. It would help protect boats moored adjacent to private property from the wakes of passing boats and cut down on noise. It would also help prevent theft and vandalism.

 

Fact: Most of the work being done by the state of Florida to protect manatees is fueled by donations, either from the Save the Manatee Trust Fund (the repository of revenues from the sale of manatee specialty automobile license plates) and the Motorboat Revolving Trust Fund, which takes a portion of Florida boat registration fees. Almost no state general revenue is used for the protection of manatees. Save the Manatee Club, a private nonprofit organization, receives no money from the sale of the specialty license plates and relies on donations to fund its conservation work. (9)

 

FACT: Fossil remains of manatee ancestors show they have inhabited Florida for about 45 million years. Modern manatees have been in Florida for over one million years (probably with intermittent absences during the Ice Ages); i.e., a lot longer than people have lived here. The present Florida manatee (Trichechus manatus latirostris) is a subspecies endemic to Florida. Genetic studies to date indicate that it is not derived from the populations in Mexico or Central America, but more likely colonized Florida from the Greater Antilles thousands of years ago, after the last Ice Age.  However, there is no evidence that manatees are now entering Florida from Central America, the Caribbean, or anywhere else.  The manatees in Florida today have every right to be considered Florida natives.(10)

 

FACT: There is no evidence to indicate that Florida's economy will be negatively affected or has been negatively affected because of the adoption of manatee protection measures. In a 1997 study by Dr Frederick Bell an economist at Florida State University and Mr. Mark Mclean, shoreline property values in Broward County were compared where manatee zones were present or absent in the adjacent waters.  The results of the study show that contrary to this widespread myth, with all other factors being equal, shoreline property values went up by as much as 15% when there was a manatee slow speed zone adjacent to the property. (11)

 

Fact: The marine industries were allowed by the court to intervene in the federal lawsuit that Save the Manatee Club et al brought against the U.S. Army Corps of Engineers and the U.S. Fish and Wildlife Service.  Representatives from the National Marine Manufacturer's Association, the Marina Operators Association of America, Association of Florida Community Developers and the Marine Industries Association of Florida participated in negotiations with the plaintiffs and the government agencies (defendants) in this case and signed off on the negotiated settlement agreement. The USFWS has held a series of hearings on their proposed rules and will hold more in the future.

 

Although the marine industries were denied the ability to act as intervenors for the Florida Fish & Wildlife Conservation Commission (FWCC) in Save the Manatee Club vs. Allan Egbert, (Executive Director of the FWCC), the FWCC is in the process of holding public meetings and hearings on the proposed protection measures in Brevard County stemming from settlement negotiations, and will continue to hold hearings on any future measures proposed.

 

Further, every manatee slow speed zone rule that has ever been adopted in the state of Florida has undergone a rigorous review by the general and boating public. This review has included noticed public workshops and hearings.

 

Fact: Save the Manatee Club and the U.S. Fish & Wildlife Service put together two independent lists of possible locations for additional manatee sanctuary and refuge designation. These were lists that identified waterbodies that, based on their documented manatee use, should be investigated when identifying locations to site new sanctuaries or refuges.   The list did not delineate the specific areas within these waterbodies that might be considered by the Service for additional sanctuary/refuge designation.

 

It is important to note that the vast majority of existing sanctuaries and refuges are relatively small areas with the highest level of protection (sanctuary) being reserved for areas that are the most sensitive and critical manatee habitat. 

Specific sites will eventually be chosen within these waterbodies and they will be picked based on scientific data which will include high manatee use and/or mortality and the abundance of specific habitat features such as the existence of seagrass beds, fresh or warm water sources, or quiet areas manatees are already known to use to satisfy their biological needs. The vast majority of the state's waters will remain unregulated to be enjoyed by recreational and commercial users.

 

Fact: There is no data to indicate that fewer boats will be purchased or that the marine industries will suffer huge economic losses if additional manatee protection measures are adopted. On the contrary, the number of boats registered in Florida has continued to increase over time. (12)

 

Fact: Although power plants probably have acted as attractants to manatees who use the plant effluents as winter warm water refugia, the effluents are critically important to manatees during cold spells. Manatees are susceptible to cold stress and cold-related diseases and often die when ambient water temperatures drop below 68 degrees Fahrenheit.

 

As coastal development pressures in southeast and southwest Florida have pushed manatees further north, power plant effluents have played a critical role in manatee protection. Even without the existence of power plants, manatees would still use Brevard waters as they offer many habitat features manatees need.

 

Fact: Past and recent surveys indicate that the majority of boaters support manatee protection measures. Further, the bottomlands of Florida's rivers and streams are public lands and are managed by the state for the benefit of all the public, not just the boating public.

References
(1)   Florida Manatee Status Statement by the Manatee Population Status Working Group, 28 April 2000.
(2)   Ackerman, B.B.  1995.  Aerial surveys of manatees:  a summary and progress report. Pages 13-33 in T.J. O'Shea, B.B. Ackerman, and H.F. Percival, eitors. Population biology of the Florida manatee.  National Biological Service Information and Technology Report 1.
(3)   United States Fish and Wildlife Service.   1996.  Florida Manatee Recovery Plan (Trichechus manatus latirostris).  [Second Revision - Originally approved April 15, 1980].  Prepared by the Florida Manatee Recovery Team for the U.S. Fish and Wildlife Service, Atlanta, Georgia.  160 pp.
(4)   Marmontel, M.  1993.  Age determination and population biology of the Florida manatee, Trichechus manatus latirostris.  Ph.D. Dissertation, University of Florida, Gainesville, 408 pp.
(5)   Ackerman, B.B., S. D. Wright, R.K. Bonde, D.K. Odell, and D. Banowetz.  1992.  Trends and patterns in manatee mortality in Florida, 1974-1991.   P. 22 in Interim report of the technical workshop on manatee population biology (T.J. O'Shea, B.B. Ackerman, and H.F. Percival, eds.).  Manatee Population Research Report No. 10.  Florida Cooperative Fish and Wildlife Research Unit, University of Florida, Gainesville,  83 pp.
(6)   Manatee Salvage Database, January 1974  July 1986 USGS, Biological Resources Division, Sirnenia Project; July 1986  2000,  Florida Fish and Wildlife Conservation Commission, Florida Marine Research Institute
(7)   Bolen, M. E., et. Al.  1999.  A Comparison of Techniques Uses in Determining Ages of the Florida Manatee (Trichechus manatus latirostris). Abstract from the  proceedings of the 13th Biennial Conference on the Biology of Marine Mammals
(8)   Bolen, M. E.  1998.  Age Determination of the Florida Manatees, Trichechus manatus latirostris, Killed by the 1996 Red Tide Epizootic in Southwestern Florida. Abstract from the proceedings of the World Marine Mammal Conference.
(9)   Save the Manatee Trust Fund, Annual Report, 1999-2000
(10)   Sirenews, Number 34, October 2000.  Darryl P. Doming, editor Newsletter of the IUCN/SSC Sirenia Specialist Group.
(11)   Bell, F. W. And M. Mclean, 1997, The Effect of Manatee Speed Zones on Property Values, Department of Economics, Florida State University. 
(12)   Florida Department of Highway Safety and Motor Vehicles, 1976  1999, Vessel Registrations.

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