As of 1996, the International Union for the Conservation of Nature and Natural Resources (IUCN), which maintains the IUCN Red List of species threatened with extinction, listed the Florida manatee as Vulnerable to extinction based on habitat loss or degradation; harvesting for subsistence, materials or medicinal purposes; accidental mortality; and pollution effects. However, a more recent assessment, completed in 2005, proposes to list the manatee as Endangered. This assessment has not, to date, been accepted.The U.S. Fish and Wildlife Service first listed the manatee as an Endangered species in 1967, predating implementation of the Endangered Species Act of 1973. This initial listing and subsequent designation of critical manatee habitat was historic in that it was one of the first designations of critical habitat for an endangered species, and the first for any marine mammal. Manatees are also federally protected under provisions of the Marine Mammal Protection Act of 1972.Developed in 1980, the initial Federal recovery plan for manatees covered both subspecies of Trichechus manatus (the Florida manatee and the Antillean manatee, which occurs in Puerto Rico and the U.S. Virgin Islands). This recovery plan was revised in 1989 to focus solely on Florida manatees. Subsequent revisions of this manatee recovery plan occurred in 1996 and 2001. The State of Florida's Fish and Wildlife Conservation Commission downlisted the manatee from Endangered to Threatened status on June 7, 2006 under newly developed criteria for listing imperiled species. Why are manatees endangered? Trichechus manatus latirostris is endangered due to the many near and long term effects of human activities on population growth and adult survival. Habitat loss as the result of unconstrained coastal development is a major consideration, as are human-related factors such as death due to watercraft collisions, entrapment in flood gates and canal locks, entanglement in gear or lines, etc. Beyond human-related causes, natural factors such as cold stress, depressed rates of survival in young manatees, red tides, and stochastic events, all contribute to annual losses to the population that may be unsustainable over the long term.Because manatees are long-lived, their natural history and population biology operate over extended time periods (Marmontel et al. 1997). The manatee is characterized as a species with a low maximum rate of potential increase (USFWS 2001). It is slow to mature, generally produces only one offspring per pregnancy, has long periods of offspring dependency, and long interbirth periods. Thus, like other large mammals, for populations to remain stable over time, high rates of adult survival are vital.Survival rates, however, are depressed in both young manatees and in adults.Marmontel et al. (1997) analyzed population viability in the manatee and noted survival rates between 1976 - 1991 were low among the youngest calves, with half of the manatee carcasses recovered recovered under the Florida Fish and Wildlife Research Institute's Marine Mammal Rescue and Recovery Program belonging to Age Classes 0, 1 and 2. Under the provisions of this program, manatee carcasses are recovered and transported to the State's Marine Mammal Pathobiology Laboratory in St. Petersburg for necropsy and determination of cause of death. Using data from 1974 - 2005, Florida Marine Research Institute (FWRI 2006) reported 5,725 manatee carcasses recovered statewide. Of this, 1,199 (21%) deaths occurred in manatees measuring less than 5 feet in length.From 1985 - 2005, there were a total of 4,850 manatee carcasses recovered in Florida. USFWS (2001) reported a 6.0% annual increase in manatee deaths between 1976 - 2000. Note that 1996 was the deadliest year for manatees, followed by 2005 and 2003. In 1996 and 2005, red tides may have increased mortality to greater levels than was observed in other years (FWRI 2006 press release). A large red tide outbreak on Florida's West coast killed 151 manatees in 1996, while red tides were believed to be responsible for the deaths of 81 manatees in 2005. However, most of the increase in manatee mortality is attributable to increased watercraft-related death and perinatal death (USFWS 2001; Marine Mammal Commission 1993).The Importance of Watercraft-Related Mortality: Because the manatee is slow to mature and has a low reproductive capacity, population stability and growth are linked closely to adult survival rates. Marmontel et al. (1997) reported that manatee survivorship curves resembled those of exploited populations and explained this observation as being due primarily to human-related causes that account for 30% or more of total documented mortality annually. Watercraft collisions alone account for 25% of annual mortality (FWRI 2006; Haubold et al 2006; FFWCC 2003; USFWS 2001; Marmontel et al 1997) and approximately 3.5 - 5.3% of the annual observed total population (Haubold et al. 2006). Many researchers (Haubold et al. 2006; USFWS 2001; Marmontel et al. 1997; Wright et al. 1995) have emphasized that besides habitat protection, population stability and growth can be achieved by reducing watercraft-related deaths. However, all indicators show that on an annual basis, there is likely to be even greater watercraft pressure on manatee populations as Florida's human population grows and the number of watercraft increases.Florida's human population has increased 130% since 1970, and will exceed 18 million by 2010 (USFWS 2001; Bureau of Economics and Business Research 1993). Net immigration of new permanent residents to Florida is approximately 760 persons per day, with 80% of immigrants choosing to settle within 16 km (7 miles) of a coast (Bureau of Economics and Business Research 1993). Haubold et al. (2006) noted that by 2004, the number of registered boats in Florida had doubled since 1980 to over 982,000, excluding those that are brought to Florida by seasonal visitors and tourists. As of December, 2005, the number of registered vessels in all size classes in Florida was 1,010,370 (FDHSMV 2005), approximately 1 vessel for every 17 persons. Wright et al. (1995) projected that this number is expected to increase by approximately 2.9% each year, and will continue to increase in concert with increases in Florida's human population. Ackerman et al. (1995) reported that boating-related mortality in manatees increased by 10.3% annually since 1976. Additionally, the sub-lethal effects of watercraft collisions are also cause for alarm. Based on a photo identification database, more than 1000 Florida manatees are documented to have at least one healed scar caused by a boat strike. Moreover, 97% of manatees in this sample bear scars from multiple collisions (O'Shea et al. 2001; Wright et al 1995; Beck and Reid 1995). IRL Manatee Mortality Statistics: In the 5-county area of the Indian River Lagoon, manatee mortality from 1985-2005 totaled 1,414 animals. A disproportionately high amount of total mortality occurred in Brevard County with 896 manatee deaths (63%). Volusia County followed distantly with 222 deaths (16%). Martin County accounted for 134 deaths (9%), while deaths in Indian River and St. Lucie Counties numbered 104 (7%) and 58 (4%) respectively.As in other areas, watercraft collisions are the leading factor in manatee deaths in IRL Counties, with Brevard County accounting for 57% of watercraft-related deaths in the IRL and leading all Florida counties in the number of watercraft-related manatee deaths.Management and Recovery Plans: Marmontel et al. (1997) stressed that manatee management and recovery efforts must focus on retaining and improving the conditions under which manatee demography operates, with research and management priorities centered on habitat protection and reduction of adult mortality. Recovery Plans:USFWS:Trichechus manatus latirostris is Federally listed as an Endangered species under the Endangered Species Act of 1973, and was downlisted in Florida to Threatened status as of June 7, 2006. The most significant and controllable threat to manatee recovery remains human-related mortality, specifically boat strikes that cause death or debilitating injury (USFWS 2001). As a result, the challenge for managers has increasingly become how to modify human, not manatee, behavior (Reynolds 1999). The USFWS and FFWCC will both continue to evaluate needs for additional protection areas that may be necessary to achieve manatee recovery, with the goal of considering manatee needs at the ecosystem-level, thus assuring that protection regulations as well as quality and quantity of habitat are sufficient to ensure recovery of the species.Recently, both the USFWS and FFWCC have used targeted enforcement strategies in an attempt to increase boater compliance with manatee protection areas and slow-speed zones, which ultimately will reduce manatee injuries and deaths.Current priority actions in manatee conservation and protection include improved boater education, increased enforcement of existing regulations, improved maintenance of signs and buoys, compliance assessment, and periodic re-evaluation of the effectiveness of the rules. However, increased protection and enforcement efforts have generally met with vehement opposition by recreational boaters, boat manufacturers, legislators, and development interests throughout the State.Another significant problem for managers is the insuring the stability and longevity of warm-water winter refuges. Historically, manatees relied on warm temperate waters of south Florida and on natural warm-water springs throughout their range as winter refuges. However, with the increased construction of power plants and other industrial plants discharging thermal effluents, manatees expanded their winter ranges to include these sites as well. Currently, approximately 66% of the total manatee population relies on industrial sites for winter refuge from cold waters. Should the stability of these sites come into question, as could occur as the power industry continues to deregulate, then manatees in these areas could become vulnerable to escalating mortality rates. Intensive coastal development throughout Florida poses an additional long-term threat to the Florida manatee (USFWS 2001). There are three major approaches to address this problem. First, the USFWS, and the state agencies of Florida, Georgia, and the Gulf States, as well as other regional recovery partners continue to review and comment on permit applications for construction projects that could occur in manatee habitat areas so that detrimental impacts can be minimized. Second, coastal counties in Florida have been required to develop their own plans for manatee protection. Third, habitat protection is being accomplished through land acquisition. Both the USFWS and the State of Florida have taken steps to acquire new areas of critical manatee habitat for protected areas. The State of Florida has acquired important areas through several programs, most notably the Florida Forever Program (USFWS 2001).The USFWS Manatee Recovery Plan (2001) sets the long-term goals of minimizing the causes of manatee disturbance, harassment, injury and death; determining and monitoring the status of the manatee population; identification, protection, evaluation and monitoring of critical manatee habitats; facilitation of manatee recovery efforts through improved public awareness and education. There are also threats from natural events such as red tides and cold events that may require additional efforts. It is anticipated that full recovery may not be possible for another 14 years or more. Federal downlisting of the manatee will occur when the following conditions are met:1. Threats to manatee habitat or range, as well as threats fromnatural or man-made factors are reduced; minimum spring flowsin warm-water refuges are identified; critical foraging habitats areprotected; and human-caused deaths are reduced. 2. In each of the 4 regional subpopulations over 10 years, thefollowing benchmarks are achieved: the average adult survival rateis 90% or greater; there is statistical confidence that the averagenumber of adult females accompanied by first- or second-yearcalves in winter is at least 40%; and there is statistical confidencethat the annual rate of population growth equals or is greater thanzero. In August 2001, the Coastal Conservation Association petitioned the Florida Fish and Wildlife Conservation Commission to assess the Endangered status of Trichechus manatus latirostris with a view to delisting it as an endangered species. Manatee status was reviewed, but in December 2003, FFWCC postponed most listing decisions to re-evaluate the listing process. This new process was adopted in April 2005, and the manatee was reviewed under the criteria for this new process. It was found that though manatee numbers appear to have risen over the last several decades, many human-related (habitat loss, coastal development, watercraft-related mortality) and natural threats (uncertainty of future warm-water refuges, red tide events, hurricanes and other stochastic events) to the population remained. Under Criterion A, which addresses population reduction, it was found that the manatee had a 12.1% probability of a 50% population reduction within 3 generations; and a 46.5% probability of a 30% population reduction in 3 generations. It thus qualified as a Threatened species under Criterion A.Criterion B concerns the extent of occurrence and area of occupancy. It was found that the extent of manatee occurrence is approximately 7500 square miles, with an area of occupancy of 100 - 300 square miles. Manatees met the condition of a decline in area of occupancy, but the Biological Review Committee did not feel that manatees occur only in a limited number of locations, nor was their habitat severely fragmented. Hence, manatees did not qualify under Criterion B.Criterion C addresses population size and population trends. The total minimum population size for the manatee was calculated to be 2,310 adults, with no evidence of extreme fluctuation in population numbers, and no subpopulation contained greater than 90% of the total population. However, the probability of a 20% reduction in population size within 2 generations was calculated to be 55.5%; and there was a 77.1% probability of a 10% population reduction. Manatees thus qualified as Threatened under Criterion C.Criterion D concerns the number of mature individuals in the population. With a minimum adult population size of 2, 310, and an area of occupancy of 100 - 300 square miles, the manatee did not qualify under Criterion D.Criterion E addresses the probability of imminent extinction. It was calculated that manatees had an overall probability of extinction in the next 100 years of only 1%. Further, the total population is not likely to approach any of the qualifying thresholds outlined in the listing criteria; though one of the 4 subpopulations would qualify for listing if the subpopulations were considered separately. Thus, manatees did not meet the listing qualifications under Criterion E.On June 7, 2006, the State of Florida downlisted the manatee to Threatened status under Criteria A and C above.
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