National Geographic Channel
Marine ecologists from the U.S. National Oceanic and Atmospheric Administration (NOAA) are combing the eastern Pacific for clues to why the dolphin population there is not growing, despite more than a decade of conservation efforts.
One mystery is wrapped in another. Spotted and spinner dolphins inhabit tropical seas around the world along with yellowfin tuna. But only in the eastern Pacific do the tuna and dolphin regularly stay closeor schooltogether. Nobody knows why.
That tuna-dolphin connection has led to fisheries practices that devastated the dolphin population. Dolphins are a marker for the tuna. In helicopters and speedboats, fishers prowl for dolphins, then herd them toward a mother ship and encircling nets.
"When they catch the dolphins, they catch the tuna," said marine ecologist Lisa Ballance, chief scientist in the NOAA mission, based in La Jolla, California. "The dolphins are just incidental catch."
In 1990 NOAA mandated that all tuna-fishing boats must have an observer on board if companies want their products to qualify for a "dolphin safe" label. The label means that no dolphins were captured or killed for the catch.
The label was a response to the public outcry after estimates that populations of spotted and spinner dolphins had plummeted by 75 percent since the tuna fishery started targeting dolphins in the 1950s.
Congress authorized NOAA to track the dolphin populations to make sure that they rebounded. "We've discovered something we didn't expect," Ballance said. "There's no recovery at all [from ten years ago]. Now we're trying to find out why."
The research area is a vast triangle7.7 million square miles (19.9 million square kilometers)from southern California to Hawaii to Peru. On their recent mission, the NOAA research vessels David Starr Jordan and McArthur plied these seas for four months.
For the scientists aboard, the workday began at 4 a.m. At sunrise, six marine observers stationed themselves at high-powered binoculars mounted on the bridge, where they remained until sundown.
"We're out there to look for trends in the dolphin population, but we also try to get in as much other science as we can," said Bob Pitman, another NOAA marine ecologist. "We take notes on whales, sea turtles, and whatever else we find."
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