Saving dolphins by scaring them
Every year tens of thousands to hundreds of thousands of dolphins die in fishing nets as unintended catch. Some of these deep drift nets are more than a mile long. No wonder that they are sometimes called "curtains of death". Dolphins do not recognize the fish net as a danger. They may try to get some of the fish or they may swim into the net by accident. Once they get tangled, they panic, and a fight for life begins. If they cannot free themselves and surface to breathe, they will suffocate and die. If a dolphin is lucky and free himself, some of the net may stay attached to his body and hinder him in his movements. Or he may swim away with injuries; sometimes serious cuts. In the fight for life and death, the tangled dolphin may cause considerable damage the nets. For the fisherman it also means much work to get the dead dolphin out.
A Dutch company recently came up with a technical solution for the problem: they developed the "Pinger".
Dolphins are very smart but also very curious. The idea was to develop an ultrasonic sound that would scare dolphins. Small transmitters could be attached to the fish nets. The scaring noise could keep the dolphins at a distance from the nets. The transmitter was named "Pinger".
The Pinger consists of a specially developed ceramic crystal (transducer-element) that transmits a high-frequency sound. A rechargeable battery pack provides the energy. It is all molded in plastic able to resist any pressure. The transmitter starts working immediately when it makes contact with salt water.
The determination of appropriate sound was not a simple task. There are many types of dolphins who may react in different ways to different impulses. Eventually, an ultrasonic whistle tone was found that scares enough dolphins and other mammals.
For every kilometer of net, four pingers are needed to cover the right range to keep the nets clear. The transmitters are very simple to use. They are relatively cheap. Fisherman worldwide could use them without any problems. It saves the costs of damaged nets. It saves the life of hundreds of thousands of dolphins.
