Seeing in the dark: A review of the use of side-scan sonar to detect and study manatees, with an emphasis on Latin America

Manatees are aquatic mammals that live in a variety of environments. Many of those shallow water environments have murky water, making detection using traditional visual surveys very challenging. Side-scan sonar was first proposed as a tool to detect and study manatees in these complicated habitats in 2005. Here, we summarize the use of this tool from 2005 to 2022 by searching the available literature. Our literature search revealed that this tool is being widely used in more than 20 locations and over 15 countries. All three manatee species are being studied with side-scan sonar. It is most useful in murky freshwater habitats that are not too deep or open (e.g., large lagoons or lakes), where visual surveys are not effective. Most studies used side-scan sonar in combination with other methodologies such as passive acoustics and indirect evidence. Work is still needed to standardize the use of this technique so that image interpretation can be reliable, and results can be compared between studies. However, most studies indicated that this tool is essential in murky water habitats and provides one of the best ways to detect and study manatees.