Fertilizer Increases Steelhead British Columbia Biologists Report Dramatic Changes

Despite everything weekend gardeners have heard, it’s not always bad when lawn fertilizer makes its way into lakes and rivers.

Usually, but not always.

After 10 years of purposely releasing fertilizer into a Vancouver Island river, British Columbia biologists say they’ve seen a dramatic increase in the steelhead population. The same population boom hasn’t happened on nonfertilized streams, said Pat Slaney, provincial watershed restoration manager.

B.C. biologists are so impressed, they’ve ordered 34 tons of fertilizer briquets to scatter this spring in as many as 25 island rivers. U.S. biologists haven’t yet experimented with fertilizer, but some say it may hold promise.

“We’re going full-tilt,” said Ken Ashley, a provincial limnologist. “We’ve got a rack of rivers where the steelhead are on the road to extinction unless we do something fast.”

The hope, Ashley said, is to bring back salmon runs that would then load streams with phosphorus and nitrogen the way nature intended: through their own rotting carcasses.

Salmon die after they spawn. A growing quorum of scientists believe the dead fish provide nutrients necessary to the next generation of salmon, as well as to bears and other critters, trees and other plants. Those nutrients come from the sea and aren’t available in the large quantities in the forest.

A recent study published in the journal Fisheries concludes there’s a dramatic shortage of marine nutrients in Northwestern states due to declines in salmon. The situation is nearly as dire in British Columbia, said Slaney.

Biologists in Washington and Oregon are fighting nutrient depletion by littering streams with the carcasses of hatchery fish. The Washington Department of Fish and Wildlife last year distributed more than 100,000 dead fish, said Hal Michael of the agency’s hatcheries division. But there aren’t nearly enough rotting fish carcasses to go around.

So far, Michael said, the United States has not tried fertilizing rivers. His request last year for a federal grant to study the idea was denied.

Partly, Michael said, fertilizers haven’t been tried because of anti-pollution regulations. The Oregon Department of Fish and Wildlife had to get a pollution discharge permit just to scatter carcasses, he said.

“There’s a large regulatory difference in the two countries,” Michael said.

Also, he noted, many Washington rivers that flow through urban areas or farm lands suffer from nutrient overload. That can lead to ugly rafts of floating algae that rob the water of oxygen.

Such pollution in the Spokane River led Spokane to ban laundry detergents containing phosphates in the 1990s. It prompted Liberty Lake residents to spend millions of dollars building a sewage treatment plant in the 1980s.

To prevent such pollution, folks with homes on lakes or rivers often are warned not to overfertilize their lawns and to clean up pet excrement on beaches. Ranchers are asked to keep their cows out of rivers.

But the reverse problem occurs when salmon disappear from rivers or when dams prevent nutrients from flowing downstream, said Ashley.

British Columbia’s first success with fertilizer came on Kootenay Lake, just north of Idaho.

Dams on the Kootenai River in Montana and Canada block nutrients that feed the lake’s plankton. Plankton are vital to kokanee, a landlocked sockeye salmon. The diminutive kokanee feed massive Gerard rainbow trout sought by fishermen.

By 1991, the kokanee and rainbows were disappearing. Kootenay Lake’s water was so devoid of life, a boater could see 65 feet into the clear water.

Biologists, who were doubtful anything could save the fishery, tried dumping liquid fertilizer from a barge as a last resort. The number of spawning kokanee increased from 250,000 in 1991 to 400,000 in 1992. Buoyed by that success, biologists stepped up the fertilization and more than 2 million kokanee spawned in 1999, said Ashley.

Asked whether anything other than fertilizer could account for the turnaround, Ashley could think of only one thing: “Divine intervention.”

Fertilizing streams is more difficult than fertilizing lakes because the current carries away the nutrients as soon as they’re released. Ashley and other researchers have tried a variety of techniques in the past, including slowly dripping liquid fertilizer from tubes.

Lasco Inc. of Cleveland solved the problem by making briquets from a granular fertilizer the company normally sells to golf courses. The briquets settle on the bottom and release nutrients over a period of months, said Lasco Vice President Breck Denny.

As a trout fisherman, Denny said he’s excited about playing a role in salmon restoration. As a businessman, he sees a potential new market for Lasco’s product.

Lasco plans to sponsor a symposium in Portland next year. B.C. biologists will be invited to speak, said Denny, who hopes they’ll convince U.S. agencies to consider artificial fertilization of depleted rivers.

But Ashley and Slaney caution that fertilizer alone can’t bring back a salmon run decimated by loss of habitat to development, agriculture or dams.

“It’s just one part of the puzzle,” Slaney said.

This sidebar appeared with the story: THE RESULTS

Biologists dumped liquid fertilizer in Kootenay Lake in 1991. The number of spawning kokanee increased from 250,000 to 400,000 in 1992. Biologists stepped up the fertilization and more than 2 million kokanee spawned in 1999.