Hobbies And Interests
Seismic Surveys
The process of seismic surveying utilizes multiple specialized ships. These ships drag a trawl or long line connected to a formation of large air guns that produce immense sound waves. These sound waves are shot at the ocean floor and bounce back to the ships. The information can then be analyzed to draw the makeup of the sea floor. The sound intensity from this procedure can reach as high as 250 decibels (dB), and the trawling can span hundreds of miles of ocean. A seismic survey takes about two or three weeks. A jackhammer has a sound intensity around 120 dB, and this can damage human hearing within seconds.
Effects on Marine Mammals
The effects of seismic surveying on marine mammals are noteworthy. As most terrestrial animals rely principally on the sense of sight, marine mammals use hearing as their principle sense. Marine mammals use sound to find food, find migratory paths, communicate and avoid predators. Researchers have documented that the sound intensity generated by seismic surveys alters whale and dolphin behavior. According to the Alaska Marine Conservation Council, "Numerous scientific studies have solidified what Eskimo subsistence hunters have known for years: that whales avoid expansive areas where seismic surveys are being conducted."
Effects on Fish
Fish are also affected by seismic surveys. Physical damage from this procedure to fish ears and swim bladders leads to abnormal fish behavior. Scientists have also documented that fish may display an inhibition at catching food and an increased vulnerability to predators. The migratory and breeding patterns of some fish species, such as salmon, has also been documented as being negatively affected. Close range seismic surveys can cause death in adult male fish, fish larvae and fish eggs.
Effects on the Fishing Industry
Because of its negative effects on marine life, seismic surveys also negatively impact the fishing industry. Researchers and fisherman have documented the effect on catch sizes relative to seismic surveys. When companies undertake a 250 dB seismic survey, fisherman and scientists note a reduction in catch size by up to 70 percent in some cases. Reduced catch sizes can last as long as five days beyond the end of the seismic survey. Scientists believe the catch sizes diminish because the seismic surveys cause the fish populations in the area to act erratically, not biting hooks and swimming deeper than usual to avoid the sound.