The decade will end on a low note for conservationists working to protect Florida's endangered population of manatees, as the Florida Fish and Wildlife Conservation Commission's Fish and Wildlife Research Institute documented 419 manatee carcasses in state waters so far this year, the most for any year since record-keeping began in 1974.

That number accounts for 12.5 percent of the entire population, clearly an unsustainable rate. Most of the deaths could be directly attributed to human causes, with boat strikes constituting as much as 30 percent of the fatalities, which alone is three times greater than natural causes.

One of the reasons that manatees are so slow and docile is that they have no natural predators, which means that their biggest threat comes from human development. Aside from boat strikes, manatees are routinely crushed or drowned in canal locks, hurt and entangled by fishing line and hooks, and they are highly vulnerable to deadly blooms of "red tide" algae.

Meanwhile, most of the natural deaths this year were blamed on colder than average waters, leading to a high mortality rate among infant manatees.

Aside from the bad news at the end of this decade, the overall manatee population is believed to have increased slightly over the last several decades, with a reasonably stable population of just over 3,500. But developers and the boating industry have been lobbying for looser restrictions in recent years, which could continue to threaten the conservation of these subtly charismatic mammals in years to come.

To report a dead or distressed manatee, you can call the FWC Wildlife Alert Hotline at 888-404-FWCC (3922).

12.5% of all Florida manatees killed in 2009
As many as 419 manatees have been found dead since Jan. 1, the highest number on record for a calendar year.