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Indian Inver County Nlnnatee Protection and Boating Snfgv Comprehensive Management Paan MANATEE MORTALITY Threats to Manatees There is general agreement among researchers and state and federal agencies that a fundamental threat facing manatees is human -induced mortality, both through direct impacts and habitat destruction. While watercraft -related mortalities are the leading cause of human - induced mortalities, marine debris is another cause of injury and death of manatees and other inhabitants of the IRL ecosystem, The amount of marine debris in the marine habitat has increased as a result of increased boating activities. Items such as fishing line, plastic bags, crab traps and abandoned nets increase the chance of human -related manatee injury or death. Furthermore, water -borne pollutants cause indirect harm by reducing the amount of SAV. To date, a causal relationship between pollution and manatee mortality has not been documented, but exposure to water -borne pollutants may cause chronic problems for manatees, such as impaired immune system health. Finally, feeding manatees causes harm by: reducing manatees' natural fear of humans; altering normal manatee migration and behavior; interfering in the mother -calf relationship; causing food -related illness; and bringing manatees into areas of increased exposure to humans and water -related activities. Statistics From 1974 to 1998, there were 3501 manatee mortalities documented throughout the State of Florida. Of those, 64 (1.8 per cent) manatee mortalities were recorded in Indian River County. I-luman-related causes of death include: watercraft collisions, drowning in nets, ingested debris, and manatees being crushed by water control structures. Of the total manatee mortalities recorded in Indian River County between 1974 and 1998, twenty-seven (29.7) percent (19) were the result of human -related causes. All of these human -related mortalities were attributed to collisions with watercraft. This compares to the watercraft -related mortality average of 23.6 per cent (828) for the entire state over the same timeframe. Some factors influencing watercraft collisions include; watercraft size and type, on -water traffic patterns and their overlap with manatee travel and feeding areas; channel depth and configuration of water bodies; and marina/boat facility siting. The cause of death could not be expressly identified for approximately 20.3 per cent (13) of manatee deaths. Thus, these deaths were reported as .'undetermined". In addition, one manatee carcass, or 1.6 per cent of the County's manatee deaths, was verified but not recovered. "Perinatal" or dependent calf deaths represented 35.9 per cent (23) of the collected carcasses. The remaining category, "natural" causes, accounted for 12.5 per cent (8) of the total manatee deaths in Indian River County during the period from 1974 to 1998. According to FWC-FMRI data, 1996 was a record year for mortalities in Indian River County and the State of Florida. In 1996, there were a total of 60 watcreraft-related deaths recorded in the State of Florida. Of these, four (4) watercraft -related deaths, approximately 6.6 per cent of state's total for 1996, were recorded in Indian River County. In 1997, a total of seven (7) manatee deaths were recorded in the county. Of these deaths, only one (1) in Indian River County (14 per cent) was watercraft -related. Statewide, there was a total of 54 watercraft - related deaths in 1997. Community Development Department Page 22