New Science Could Benefit Sockeyeby Rocky Barker
Idaho Statesman, June 5, 2013
A radio telemetry study is providing data that could help biologists figure out new ways to aid the endangered salmon
Transmitters a half-inch long implanted in 4- to 6-inch juveniles and a network of antennae are revealing secrets about why half of all Idaho sockeye die before they ever get to a dam.
Predatory birds and bull trout are probably eating the young sockeye just after release, according to data generated by a radio telemetry study by the National Oceanic and Atmospheric Administration.
But about 10 percent more sockeye salmon from the Sawtooth Hatchery in the Sawtooth Valley vanish shortly after their release than do fish from the Oxbow Hatchery along the Snake River transported to the same release site below Redfish Lake.
Why the difference?
Turns out that the Sawtooth fish were released during the day; the Oxbow sockeye were released at night.
So Idaho Department of Fish and Game biologists plan to release Sawtooth sockeye at night this year to see whether that cuts the losses.
"We want to identify areas or hot spots where mortality might be occurring and tell whether there's anything we can do to increase survival," said Mike Peterson, the senior Idaho Fish and Game research fisheries biologist for the sockeye program.
BACK FROM EXTINCTION
The sockeye migrates 900 miles and climbs 6,500 feet on its way from Idaho to the Pacific and back. The juvenile fish, known as smolts, face a hazardous start of their journey down the Salmon and into the Snake River before they get to Lower Granite Dam in Washington state.
In the late 1800s, so many thousands of sockeye returned to Redfish Lake every year that a cannery was proposed. But by 1991, the sockeye was listed as an endangered species. The following year, just one - dubbed Lonesome Larry - returned to Redfish Lake.
A joint captive-breeding program between NOAA Fisheries, Idaho Fish and Game and the Bonneville Power Administration brought the salmon back from the brink of extinction. Although just 243 sockeye returned to the Sawtooth Valley in 2012, more than 650 sockeye had returned annually to the Sawtooth Valley since 2008. That included 1,355 in 2010, the most since the 1950s, when four dams were built in Washington.
The new research found that sockeye average around seven days to travel 460 miles from Redfish Lake Creek to Lower Granite Dam.
Before the network was erected in 2011, the only way to follow the sockeye was to detect the fish - and its tiny passive integrated transponder (PIT) tags implanted at the hatchery - as they passed a dam.
The team uses both PIT tags, which emit signals only when they pass detectors, and small radio telemetry tags that actively broadcast coded signals identifying each fish as it swims downriver.
Advances in batteries and electronics have shrunk the size of the tags - they weigh about as much as a dime - which allows researchers to safely implant the devices in smaller fish.
GOING TO WHERE THE FISH ARE
Today, the network follows the fish where biologists couldn't before.
Gordon Axel of the Northwest Fisheries Science Center's Pasco, Wash., research station leads the team that installed the sophisticated network to follow the sockeye smolts through Idaho's wild heart. He said the telemetry system scans nine different frequencies for fish passing each fixed site.
In 2012 and again this year, the NOAA team positioned telemetry receivers at 21 sites along the Salmon and Snake rivers, studying the rivers in sections to identify where the sockeye die. The team also used mobile receivers on backpacks to track individual fish even more closely.
"What we learn can be applied to release strategies, increasing the probability of survival to aid adult returns back to the Redfish Lake," said Jonathan McCloud, BPA's project manager.
BPA is paying to build a new sockeye hatchery in southeast Idaho near Pocatello, which will raise as many as 1 million additional sockeye smolts for release each year.
Those fish won't recover the sockeye populations alone - naturally spawning fish are the key to that. But biologists hope that increasing the number of smolts that survive the gantlet of predators and dams increases the number of sockeye that spawn naturally.
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