Pings Provide Exacting Fish Countby Joe Rojas-Burke
The Oregonian, August 4, 2004
A virtual bar-coding system at the Columbia River bar
that gives focus to salmon recovery efforts encounters setbacks
ILWACO, Wash. -- At the mouth of the Columbia River, where ocean waves collide with an immense outgoing current, a small boat bobs on the infamous bar, destroyer of whole ships.
"We're right there Geoff, you should be able to hear it from here," shouts Lynn McComas, the scientist at the helm of the Barracuda, a 26-foot government research vessel. Before Geoff McMichael can answer, a swell pitches the boat sideways at a steep angle, throwing a laptop computer and other equipment to the deck.
"I can't think of a more difficult place to ground-truth this," sighs McMichael, who quickly puts his gear in order.
Beneath the roiling shallows of the treacherous bar, about 20 feet down in the murky green water, the scientists earlier this summer had suspended two rows of automated electronic sensors to "listen" for baby salmon passing by. The sensors, called hydrophones, pick up recorded pinging signals sent from tiny transmitters implanted in a thousand smolts -- and in doing so form a virtual supermarket-style bar-coding checkout station.
Until now, no one has been able to track what happens to salmon during their final migration to the sea once they pass Bonneville Dam, 146 miles upriver. That's important information, however. With an exacting count at the river's mouth, researchers hope to gain answers to questions about how the dams may be hurting salmon and steelhead, including the dozen stocks listed by the U.S. government as threatened or endangered.
The lack of scientific certainty about dam operations came clear last week, when a U.S. district judge in Portland ordered a halt on plans to boost power production this summer to avoid harm to threatened Snake River chinook salmon. Overruling the U.S. Army Corps of Engineers and the National Marine Fisheries Service, which said no harm would come to threatened salmon, the judge granted the order sought by conservation groups, Native American tribes and, significantly, Oregon Gov. Ted Kulongoski.
Much is at stake. In the effort to sustain and rebuild salmon runs, the federal government now spends more than $700 million a year in the Columbia River Basin. The heavy spending, however, still has not turned things around for many stocks, particularly those bound to the farthest upriver reaches of the Snake River, past eight large hydropower projects.
The Corps of Engineers runs the Columbia's extensive system of hydroelectric dams and spent close to $2 million to develop the new tracking system, including a set of four detectors linked by cable to a monitoring station on West Sand Island, an oversized sandbar.
To help the fish, the corps collects many ocean-bound juveniles at upstream dams, loads them into tanks, and transports them by barge or truck to be released back to the river below Bonneville Dam. But studies have shown that -- for reasons that remain unknown -- an unusually large proportion of transported fish never return from the ocean to spawn.
"Barged fish, despite their surviving well below Bonneville, fail to return at rates that would reverse population declines," said Earl Weber, a fisheries scientist with the Columbia River Intertribal Fish Commission, an agency representing Native American tribes with treaty rights to salmon that along with many conservation groups want the government to remove four Snake River dams to help recover salmon.
Weber and other critics of federal salmon policy think collecting and transporting fish inflicts stresses that result in injury or death days or weeks after the fish are released back to the river.
"Where that takes place, we don't know," Weber says. If fish succumb after entering the sea, then even a tracking system along the Columbia River bar couldn't supply definitive answers.
Onboard the Barracuda, McComas, a fisheries biologist with the National Marine Fisheries Service, talks excitedly about the capabilities of the new system, which was developed in cooperation with McMichael and others at the Battelle Pacific Northwest National Laboratory in Richland, Wash. If barged salmon suffer delayed deaths in the lower river or estuary, detectors at the mouth of the river should be able measure it.
"We'd like to know how much mortality is due to travel through the hydropower system, then try to manipulate the system to reduce the causes of that mortality," McComas says.
But at the moment, an unforeseen glitch has emerged: attacking mud. Tons of sand and mud moved by the river and tide appears to have buried many of the tracking devices.
"All's well" signal
McMichael drops a hydrophone over the side of the boat by its cord. A coded message, 44RL, repeats in a rapid scroll across the screen of his laptop computer. It's an "all's well" signal from one of the 11 detectors.
"So we're right over that guy," McComas says. But the detector stubbornly refuses to surface when McMichael transmits a command signal to a motorized releasing clamp.
The detectors float about 15 to 25 feet below the roiling surface of the river and about 15 feet from the river bottom, tethered to a heavy steel anchor. On the deploying mission, rough seas forced the team to quit before placing all of the devices. After several weeks, only three recorders work as planned, bobbing to the surface on command. Two recorders have disappeared completely. The rest refuse to surface.
Weeks earlier researchers intercepted a thousand young chinook at Bonneville Dam and implanted tiny transmitters that send out a high-frequency pinging undetectable to human ears. The detectors placed at the river's mouth listen for the pinging, and record the time and place of each detection on a flash memory card. Without the card, the data can't be recovered.
McMichael falls silent during most of the trip back to the port at Ilwaco.
Encouraged by the devices that are working and sending a locating signal, the researchers plan to return with a grappling hook to drag the water for their quarry. And they manage to bag one. Ultimately, it takes two boats dragging a weighted cable between them to bring up the last three detectors.
Nine of 11 retrieved
In all, the researchers manage to recover nine of the 11 "nodes," and none has lost data.
"We have detections from several hundred fish, of the 923 released, and have some great new insights about how long it takes these fish to get to the ocean from Bonneville Dam," McMichael says. Based on a preliminary analysis, he says juvenile chinook take about three days to make the trip. The trial run also shows its possible to pinpoint where in the river channel fish migrate, and how tides and daylight affect their entry into the ocean.
Assuming funding comes through, the researchers expect to place a larger set of hydrophones next year and complete a full survival study on juvenile chinook salmon from Bonneville Dam to the ocean.
"At the end of all this, we'll have a monitoring function to see how change in the management of the hydro system and changes in hatchery releases affect survival in the lower river," McMichael says.
learn more on topics covered in the film
see the video
read the script
learn the songs