Spin-off technologies from the cold war—sonar, satellite data and
the Global Positioning System (GPS)—have led to an unprecedented
decline in fish stocks worldwide, according to a study led by
researchers at the University of British Columbia (UBC) in Vancouver,
Canada.
With these technologies fisherman now have an
unprecedented view of the ocean—enabling them to guide their nets
around sea mountains, drop them into deep ocean abysses, and navigate
almost every rock pile like an underwater video game.
The total weight of tablefish—species eaten by man—in the oceans has declined by a total of 85 percent in the last century and continues to decline at 2 percent or more per year, said Villy Christensen of UBC. Many species are being hunted right down to the last fish.
At the end of the cold war, the Navy declassified sonar-mapping technologies that were far superior to their civilian counterparts. The United States Geological Survey then used this technology to produce exquisitely detailed three dimensional maps of the ocean floor.
Now the USGS is enthusiastically using this sonar technology to map the seabed, revealing intricate details of underwater landscape which are then open to exploitation [by fishermen], said Callum Roberts, of the University of York in the England, at a meeting of the American Association for the Advancement of Science last week in Boston.
The military also declassified a highly accurate version of GPS that was previously unavailable to civilians, said Roberts.
The combination of ultra accurate GPS data and ocean floor maps has been devastating. With sonar maps fisherman can identify the best regions to fish and the improved GPS directs their ships precisely to that spot.
Fishermen can now drop nets into holes and crevices with astounding accuracy. Or hover precisely over sea mountains and essentially scoop out every last fish, said Daniel Pauly, also of UBC.
But GPS data is not the only satellite data that gives fishermen the upper hand. The National Oceanic and Atmospheric Administration (NOAA) releases a daily fax to Atlantic swordfish fleets with satellite pictures revealing sea-surface temperatures around fishing grounds.
Big fish—like swordfish and bluefin tuna—are attracted to fronts where cold and warm waters meet. The satellite data guides the fishermen directly to these fronts for a fishing frenzy.
In addition to sonar-produced maps, many fishing vessels now carry sonar to locate schools of fish. Some nets are even outfitted with sonar to allow fishermen to steer their nets around obstacles and keep fishing lines at the same depth as their target.
The bluefin tuna trade is so lucrative—one fish fetches $10,000 or more in Japanese fish markets—that fishermen even hire pilots to cruise around in spotter planes to locate a school of tuna, which at six to nine feet long, are easy to spot.
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