Manatees are tropical marine mammals that live in a wide variety of aquatic habitats ranging from coastal
marine areas to freshwater lakes and rivers located hundreds of kilometers inland. All manatee species are currently
characterized as Vulnerable by the International Union for Conservation of Nature (IUCN), primarily due to
anthropogenic causes (i.e. poaching, habitat destruction, pollution, collisions with boats) and all of the environments they
live in present challenges to biologists and wildlife managers. Tropical freshwater systems are especially difficult to work
in because they are generally tannin-stained or turbid and water clarity is very restricted. Locating manatees and observing
their behavior in these environments is extremely difficult and is a major limiting factor in determining population
parameters. We summarize the use of sonar technology as an aid to detect and study manatees in these freshwater
systems. First, by a summary of what has been attempted before our efforts, followed by presenting the various ways we
have used this technology in the past 6 years to 1) detect manatees, 2) characterize manatee habitat in ways that would not
be possible otherwise, 3) identify mother-calf pairs, and 4) assist in manatee captures. Finally, we discuss the advantages
and limitations of using this technology for manatee conservation and research and present directions in which we believe
future work can be directed, such as the determination of manatee abundance via distance sampling surveys using sidescan
sonar and the use of one of the latest developments in acoustic technology, dual-frequency identification sonar.
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