Environmentally friendly parametric alarm for alerting marine mammals of approaching vessels
Marine mammals are vulnerable to boat, barge, and ship collisions. Although more commonly identified and reported in busy coastal areas, collisions are not restricted to shipping lanes or shallow water environments. A common denominator is that they all occur near the surface. Here the acoustical laws of reflection and propagation significantly limit the ability of marine mammals to hear and locate the sounds of approaching vessels. Acoustic measurements from controlled ship passages through vertical hydrophone arrays demonstrate the confluence of factors that poses auditory detection challenges for both whales and manatees. A highly directional, environmentally-friendly, low intensity underwater parametric alarm has been developed to mitigate these challenges & safely alert marine mammals of approaching vessels. The efficacy has been demonstrated with wild manatees. Ninety-five percent of manatees during alarm-on trials elicited avoidance reactions while only 5% of manatees during alarm-off trials elicit...