Tuesday, February 8, 2011

Hydrophones Help Locate Endangered Whales


By Mark Floyd
Scientists using undersea hydrophones have documented the appearance of endangered right whales in a region east of Greenland, where they historically had been hunted but were thought to be extinct. The scientists recorded more than 2,000 whale vocalizations from 2007-08, and since have identified them as right whales and mapped the geographic origin of those recordings. This mapping shows that the whales are using an area where ships commonly pass while in transit between the United States and Europe. And more shipping may take place as northern regions become increasingly ice-free. Results of the research were published this week in the journal Biology Letters.
Lead author David Mellinger of Oregon State University said the use of hydrophones enables scientists to “listen” for whales in remote areas where visual observations are difficult to conduct. Right whales have unique vocalization patterns that allow scientists to differentiate their calls from those of other whales.
“In the last 50 years, there have only been two confirmed sightings of right whales in the Cape Farewell Ground, which is about 500 kilometers east of the southern tip of Greenland,” said Mellinger, an associate professor at OSU’s Hatfield Marine Science Center in Newport, Ore. “The weather there makes it almost impossible to conduct regular surveys.
“But it was an important area historically for the whales, and we needed to determine if they were still using it,” he added. “The hydrophones showed that not only are they using the Cape Farewell Ground, but that they’ve broadened the range of where we’ve known them to be in the past.”
The North Atlantic right whale is among the rarest cetaceans in the world. Despite more than 75 years of international protection, scientists estimate that fewer than 450 individuals remain. Most of those are a “western stock” that can be seen off the East Coast of North America from Florida to the Gulf of Saint Lawrence. It is unknown whether most of the whales heard off Greenland and Iceland are from this stock.
Nor are scientists certain of the size of the population.
“We can’t tell how many individuals might have been in the area, because they aren’t individually distinctive in their vocalizations,” Mellinger said. “But we know there were multiple whales because we recorded vocalizations at roughly the same time from different locations.”
Right whales were nearly decimated by whaling in the 1800s and early 1900s, and despite a moratorium on hunting them, their recovery has been slow. The cause of many recent deaths has been anthropogenic, scientists say, especially collisions with ships and entanglement with fishing gear.
Also contributing to the journal article were other scientists from OSU, the National Oceanic and Atmospheric Administration, and the University of Iceland. Funding for the study was provided by NOAA. 



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