New parametric acoustic alarm proves effective at alerting wild manatees of approaching boats

Abstract

The efficacy of a bow mounted parametric acoustic alarm for alerting manatees of approaching boats was demonstrated with wild manatees in Florida. Two experimental conditions were tested; (1) boat approaches with the alarm-on, and (2) approaches with the alarm-off. Synchronized underwater acoustic buoys and aerial video recorders documented manatee behavior and acoustic conditions prior to, during, and after controlled boat approaches. 95% of the manatees during alarm-on trials elicited overt changes in behavior (avoidance reactions) prior to the boat reaching the focal manatee. In contrast, only 5% of manatees during alarm-off trials elicited any change in behavior prior to the vessel having to veer off. Changes in behavior observed prior to the boat reaching focal manatees was significantly greater (F = 471.9, df = 1, p< 0.01) during alarm-on trials. The mean distance at which manatees reacted to boat approaches during alarm-on trials was also 20 m compared to only 6m for alarm-off trials (F= 218.4 df =...