[3] Report Says Invasive Mussels Could Gain Foothold In Upper Snake
The potential cost of battling invasive mussel species in the Snake River could top $200 million a year, according to a new report produced by the Northwest Power and Conservation Council's Independent Economic Advisory Board [IEAB].
That's close to what BPA spends now on its direct costs for the region's fish and wildlife program.
The report said the region should expect the mussels to show up in Northwest waterways sometime soon, but there is some good news attached.
Growth of the dime-size zebra and quagga mussels seems to be limited by the calcium concentration in the water itself, which could mean the tiny invaders won't be as big a problem as in the Colorado River, where they are so prolific they have reduced water flows through trash racks at Hoover Dam by 50 percent, and threaten to clog pipes that carry water to keep turbine bearings cool and well lubricated. (see NW Fishletter 265).
"In the mainstem Columbia and Snake rivers below the Clearwater River, calcium concentrations are seasonal and within a range believed to limit mussel populations," said the July 14 report.
But above the mouth of the Clearwater, the story becomes a lot more serious, where calcium levels in the Snake and some parts of the Salmon, John Day and Pend Oreille basins "may be generally favorable for mussels."
Much of the upper and mid-Columbia contain lower calcium levels than the Snake, but the report said there were areas that could support mussel colonies--which produce free-floating larvae called "verligers" that could float downstream and lead to mussel colonization during part of the year.
But most of the Yakima and Deschutes basins would probably not support them, nor would the Columbia below the Willamette, nor the Willamette, either, said the report.
The potential worst-case scenario assumes that the mussels will colonize turbine intake screens at dams on the Snake and grow at their maximum rate. "If screens cannot be cleaned fast enough to operate within prescribed passage criteria," said the IEAB report, "then survival of migrating juvenile salmon and steelhead might be reduced."
They estimated some potential annual costs associated with controlling a zebra and quagga mussel infestation. That included $16 million to protect main cooling systems at dams on the Snake and Columbia federal dams; $3 million to $10 million at spillway gates and stilling basins, and about $3 million to keep fish passage facilities and bypass screens clear.
The IEAB's worst case include the possibility that the mussels grow fast enough at screens to impact fish survival and reduce power generation.
To keep the mussels from gaining a foothold at some 20 regional hatcheries, the economists estimated each one would need a new million-dollar filtration system, plus annual costs of $4 million to keep them all mussel-free.
The impact to recreation, boats, marinas, and water-supply facilities could be huge. The IEAB said the maximum potential cost is unknown, but put out a $50-million annual estimate, noting that it could range between tens to hundreds of millions.
The report's worst-case scenario also found that a serious infestation in the Snake Basin could adversely impact food webs and native species, possibly adding tens to hundreds of millions of dollars to recovery costs. The IEAB said more biological assessment is needed.
Since biologists are generally resigned to the fact that the invasive mussels will eventually be introduced to the region, the report says it will pay to keep this from happening for as long as possible, and that means spending more on the action plan that has been developed by 19 western states to combat the tiny invaders.
Even with stepped-up boat inspections at state borders, the mussels will probably hitchhike into the Northwest undetected on the bottom of some boat trailered from the Midwest. -B. R.
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