One method of commercial fishing is to use a trot line — a long strand of high-strength line containing baited hooks every 6 ft. Commercial trot lines can reach a mile or more in length.

The trot line is left in the water for a period of time, then slowly reeled in. The weight of the line, weight of fish that have been hooked, and resistance from the water requires massive torque from winches that reel in the trot line. Naturally, then, hydraulic winches are commonplace.

One problem is that killer whales and other marine mammals learn that the distinctive sound of a hydraulic power unit usually means a trot line is being reeled in. Noise from the power unit is transmitted through the boat's hull into the water. Because sound travels so far underwater, predators come from miles away for a free and easy meal — which cuts into the fishermens' catch. The intelligent predators have even learned to avoid hooks in the trot line by not eating the fishes' heads.

Crew members of the fishing boat installed hydraulic noise suppressors to quiet the power unit. Doing so dramatically reduced the number of fish devoured by predators. This may not be scientific proof, but the crew attributes the success to the noise suppressor.

For information on hydraulic noise suppressor from Wilkes & McLean, call (877) 534-6445 or visit www.wilkesandmclean.com