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(The Impact on Marine Mammals)
|By: LeRoy French
12 December 2008
One of Jacques Cousteau's first films was entitled 'The Silent World".
This was filmed almost a half century ago and labeled our underwater
environment as a 'Silent World'. At the time this was true. Today not so
Most marine mammals and fishes are very sensitive to sound. Noise
travels long distances underwater and potentially prevents marine
mammals and their young from finding their way. Some studies indicate
that naval sonar affects large populations of whales. Seismic airguns
used in gas and oil exploration are also a large contributor to ocean
noise. It has been shown that these airguns have affected fish from over
500 meters to several kilometers. There are 40-80% fewer fish catches
near seismic surveys.
Reef fish can be impacted by these various sounds as they rely on
normal reef noises to help them select a suitable habitat.
However, whales seem to be the most vulnerable. They have been
known to move away from feeding and breeding grounds along with
altering their migration route and in some cases fallen completely silent.
This means they are not communicating. Many have blundered into
fishing nets and in some cases have collided with ships. This is most
likely damage caused by ocean noise. Manmade ocean noise!
The three main culprits in this noise pollution are; the increase in
commercial shipping, seismic surveys and military sonar. All of these
sounds make it increasingly difficult for whales and mammals to
communicate with song. This also leads to mammal strandings.
Today shipping lanes follow the coastal routes that whales have traced
for millions of years. The result has led to beach strandings, collision, and
basically disorienting the whales so that they lose their bearings.
Here is an interesting statistic. Climate change is not helping the problem
either. ''The acidification of oceans caused by rising temperatures
reduces sound absorption by 40%, therefore allowing sound to travel
WHY DO WHALES GET STRANDED?
This has been a huge mystery for many years. There have been
hundreds of studies made on this interesting phenomenon. It is believed
that whales use a magnetic field and underwater topography to orient
themselves. This means that any deviation to this field can cause
confusion. It is not unusual for a beached whale after being returned to
deeper water to later strand on the same beach from which it was freed.
Whats happening is that the whales reference points lead them to
believe that they are heading to deeper water when in fact they are
going toward the beach. Aside from noise there are other factors
involved. Whales may be hurt or sick. Also illness and parasites can
affect their direction.
What should be noted, is that when a whale is stranded and not able to
get back into deeper water he will usually die. Keep in mind that the
whales body is supported by the sea. On land the whale's body
weighs it down and eventually may suffocate.
Global warming, pollution, plastic bags, runoff, the list seerns endless. I
realize there is very little the normal person can do about 'Ocean Noise',
but I think it is irnportant that we are made aware of how our environment
is affected by this type of pollution.
Our underwater world is no longer a 'Silent World', just ask the whales.
But shout loudly, because they're a little hard of hearing these days.