the film forum library tutorial contact

Salmon Secrets may Cast Light on Warming Trends by Staff The Columbian, November 30, 2008

WASHINGTON - They were two of the 1,000 juvenile salmon implanted with almond-sized transmitters as they headed out of the Rocky Mountains, down the Snake River bound for the sea.

Their remarkable three-month, 1,500-mile journey of survival to the Gulf of Alaska was tracked by an underwater acoustic listening network that has wired the West Coast from just north of San Francisco to southeastern Alaska. The tracking network could provide a model for a global system.

A salmon's life in the ocean has always been one of nature's best kept mysteries.

However, scientists using the Pacific Ocean Shelf Tracking network have made some startling discoveries that challenge long-held beliefs about salmon survival and raise new cautions about how global warming may affect salmon and other marine species.

"I hope it will be a revolution in the way we do marine science," said David Welch, the president of Kintama Research Corp. in Nanaimo, British Columbia, who was one of the founders of the tracking system. "I think we will make discoveries that are incredibly important and unexpected."

The transmitters, which are becoming increasingly sophisticated, smaller and cheaper, have been implanted in a dozen species, including coho, sockeye and chinook salmon, along with green sturgeon, white sturgeon, sixgill shark, salmon shark, market squid, cutthroat trout, steelhead, dolly varden and black rockfish. Eventually, scientists think they'll be able to implant the transmitters in marine animals as big as whales and as small as herring.

Signals from the transmitters are picked up by nearly 300 receivers on the ocean floor as the fish swim by. The information is eventually retrieved from the listening devices by scientists who routinely visit the eight lines of acoustic receivers by ship. The receivers don't transmit the data by satellite.

"This is a revolution in being able to study marine animals that travel vast distances," said Fred Goetz, a fish biologist with the U.S. Army Corps of Engineers who's been studying Puget Sound chinook, steelhead and bull trout. "This is a big breakthrough." Goetz said an effort is under way to permanently establish an acoustic listening line in Puget Sound near Admiralty Inlet.

Scientists are convinced the marine environment is changing because of global warming. However, no one yet understands how the changes are linked to such weather patterns as El Niño, La Niña and the Pacific Decadal Oscillation, a shift in the weather that occurs every 20 to 30 years in the northern oceans.

Tracking marine life could help document these shifts and the effects they are having on the oceans.

"Now we are getting virtually real-time information," said Jim Bolger, the executive director of the tracking network. "We are answering questions we couldn't before."

Among the findings:

• Previously, it was thought that the highest mortality rates for salmon were in the freshwater streams and rivers as they headed to the saltwater ocean. But using the acoustic tracking system, researchers found that within the first few weeks of entering the ocean, 40 percent of the salmon died. Meanwhile, billions of dollars have been spent to increase in-river survival rates of salmon through projects such as habitat improvements in spawning areas and the modification of hydroelectric dams.

• A study by Welch, which has touched off a major scientific debate, found dams may have less of an impact on salmon survival rates than previously thought. The study found juvenile salmon from the Columbia River, with its string of massive hydroelectric dams, survived their downstream migration equally or better than those migrating downstream in the dam-free Fraser River in British Columbia. Some environmentalists have insisted the only way to restore the Columbia River runs is by breaching four dams on the lower Snake River, a major tributary of the Columbia.

• It's long been thought that green sturgeon from the Sacramento and Klamath rivers in California migrated into the ocean but didn't go far. Now, using the acoustic tracking system, the green sturgeon have been found congregating off the north end of Vancouver Island at certain times of the year and then heading into the North Pacific. They've also been found in Puget Sound.