[4] No Benefit To Snake Springers From Court-Ordered 2007 Spill
A recent draft report from the Fish Passage Center shows both wild and hatchery Snake River spring chinook transported down the Columbia in 2007 did better than fish that migrated inriver.
The inriver fish had the added benefit of more spill, thanks to a court-ordered spill regime that went into place in 2006.
In fact, wild Snake River spring chinook that were barged survived to adulthood at a 15 percent better rate than inriver migrants, according to the FPC's 2009 draft Comparative Survival Study, released Aug. 31.
Hatchery spring chinook did even better. Barged springers from Idaho's Rapid River Hatchery had an 84 percent higher return rate than the stock's inriver component. Dworshak Hatchery transports have returned at more than twice the rate of their inriver counterpart, while springers released at Catherine Creek did 46 percent better in barges.
McCall Hatchery summer chinook that were barged did twice as well as their inriver brethren, and springers from the Imnaha Hatchery had a 57 percent higher smolt-to-adult return rate (SAR) than inriver migrants from that facility.
In 2006, it was a different story. Wild Snake chinook seemed to do better migrating inriver -- the smolt-to-adult return rate was 20 percent better than the SAR of the barged fish. But there wasn't much overall difference -- the SAR of the barged fish averaged 0.77 percent and the inrivers averaged 0.97 percent.
However, the SARS for some hatchery springers that were barged in 2006 turned out better than inriver return rates. The barged Rapid River Hatchery SAR was 0.58 percent, compared to 0.42 percent for inrivers, and the McCall Hatchery barged SAR was 1.16 percent, with 1.03 percent for the inriver component.
Dworshak Hatchery spring chinook that were barged had a SAR 90 percent that of inriver migrants (0.35 percent versus 0.39 percent), but Catherine Creek and Imnaha hatchery springers only did about half as well as their inriver components.
No data is available yet for the 2007 steelhead outmigration, but an August 27 FPC memo to Ed Bowles, chief of ODFW's fish division, said the added spill in the recent past has likely helped create this year's huge steelhead return.
However, according to the latest draft CSS study, hatchery steelhead that were barged in 2006 had a 49 percent better return rate than inriver migrators. Wild barged and inrivers did almost exactly the same.
In most recent years, both hatchery and wild steelhead have shown huge benefits from barging. Wild steelies had five-times-better SARs in 2005 and 14 times better in 2004, which was a relatively low flow year. -B. R.
The following links were mentioned in this story:
2008 draft Comparative Survival Study
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