Monday, March 9, 2015

Willamette Basin Steel - holding

As 'winter' winds down and we turn from winter steel pursuit to summer steelhead and trout, here is an interesting article about the Willamette and a native steelhead that occupies its waters - regardless of hatchery infusions. From the Columbia Basin Bulletin:

Study: Willamette River Basin’s Sole Native Steelhead Stock – Late Winter Run – Remains Genetically
January 16, 2015

Even after years of spawning by hatchery fish in the Willamette River basin, late winter steelhead, the only native steelhead stock in the basin, remain largely genetically untouched.

Two other runs of steelhead, one with run-timing in early winter and another in summer, come from local hatcheries on the Columbia River and have been introduced into the basin by fisheries managers to mitigate for the addition of 13 high-head dams.

Only summer hatchery fish continue to be added to the river system above Willamette Falls, but all three stocks spawn in the Willamette’s tributaries.

The native run has remained distinct likely due to factors such as timing and distance when spawning, being choosy when mating or natural selection against hybrids from fish whose ancestry began in a hatchery, according to a recent study that looked at the genetic distinctiveness of the Willamette River’s only native steelhead run, finding that the river’s native stock remains relatively pure of hatchery influence.

“Despite opportunities for gene flow among the native and introduced stocks, we found that the native stock has retained its genetic distinctiveness from the non-native stocks,” said Don Van Doornik, geneticist with NOAA’s Northwest Fisheries Science Center at the Manchester Research Station in Port Orchard, Wash. “This is an important finding because the late winter-run stock is listed as threatened under the ESA and, therefore, any negative influences the non-native, introduced stocks may be having on them must be properly investigated and accounted for.”