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Ecology and salmon related articles

Despite High 2011 Flows, Spill,
Barging Still Benefited some Stocks

by Bill Rudolph
NW Fishletter, January 9, 2014

Sending more water over spillways, in some ways, may be beneficial for juvenile salmon passage through the hydrosystem corridor. The latest results from the Fish Passage Center's ongoing Comparative Survival Study show that in 2011, inriver migrating wild Snake spring smolts fared better in the long run than their barged cohort, but some Snake hatchery stocks still benefited from the transport program.

The ratio of transport/inriver smolt-to-adult return rates for the wild spring smolts was .65, which means that the barged fish had a SAR that was 35 percent lower than the inriver migrants. In 2010, the barged fish had a T/I ratio 21 percent higher than inriver migrants.

In fact, in four out of the six years between 2006 and 2011, when court-ordered extra spill was in place, barging still showed benefits for wild springers. Barging also began later in the spring, after years of studies had shown that fish transported early did not usually benefit from the strategy.

The SAR for 2011 wild inriver migrants was .51 percent, and .33 percent for barged smolts, numbers that have been trending downward since 2008 when ocean conditions were prime, and barged fish showed a SAR nearly an order of magnitude higher, 3.01 percent, and inrivers at 2.53 percent.

Hatchery spring Chinook smolts from Dworshak did not seem to benefit from barging in 2011, either. With a T/I ratio of .63, it was not much different from 2010's .70. Since 2006, barging has shown benefits to Dworshak fish in three out of six years.

But spring hatchery smolts from the Rapid River facility showed a SAR that was 38 percent better than inriver migrants, even better than 2010's 33-percent benefit. For some reason, this stock has shown benefits from barging every year since 1994, when the CSS project began tracking survivals.

Catherine Creek hatchery smolts showed a small 5 percent boost in SARs from transport, compared to inrivers. But in 2010, the transport SAR beat the inriver SAR by more than 50 percent. From 2001 to 2011, barging benefited Catherine Creek returns in every year but one.

Inriver smolts from the Clearwater Hatchery beat transport SARs by 34 percent in 2011, but transport SARs beat inriver the previous year by 33 percent. Since 2006, barging has shown survival benefits in four out of the six years with data.

Sawtooth Hatchery smolts traveling the inriver route also fared better in the 2011 outmigration. The T/I ratio was .85, according to the latest CSS report, while barged fish had a 51 percent better SAR in 2010. From 2007 to 2011, the T/I geomean was 1.84, which means that barging was usually very beneficial during that time period.

McCall Hatchery summer Chinook, which generally show benefits from barging, did not disappoint.

The 2011 T/I of 1.44 was significant. From 1997 to 2011, the McCall stock has shown a T/I geomean of 1.59.

But 2011 smolts from the Imnaha Hatchery did better by travelling inriver, with a T/I ratio of .83. In 2010, barging showed a 27-percent benefit over inriver SARs, and from 1997 to 2011, the T/I geomean has been 1.59.

Clearwater summer Chinook also fared much better inriver during the 2011 outmigation, with a T/I of .33.

As for steelhead, The CSS report had enough data to analyze the 2010 wild steelhead outmigration, and found that the overall barged SAR (2.33 percent) was 47 percent better than the SAR for inriver migrants (1.59 percent). The benefits were clear from the T/I geomean of 2.51 for the 1997-2010 period. But hatchery steelhead did not seem to benefit from barging in 2010, with a reported T/I of .90. However, the T/I geomean for the hatchery fish was 2.34 over the 1997-2010 time frame.

So what was responsible for the lowered effectiveness of barging some stocks in 2011? It is likely that no particular reason will explain it, and some researchers chalk it up to year-to-year variability.

Relatively high spill levels in 2011 meant fewer fish were barged than usual, but still more were barged than in 2010. For example, 35 percent of the Dworshak spring hatchery Chinook were barged in 2011, but only 19 percent in 2010. Similarly, 51 percent of the Rapid River hatchery Chinook were barged in 2011, but only 23 percent in 2010.

Overall, according to NOAA Fisheries, only 35.2 percent of the spring/summer Chinook and 40.7 percent of the steelhead got a barge ride downstream in 2011. When transportation began on that May 1 at Lower Granite Dam, nearly 30 percent of the spring Chinook run and 36 percent of the steelhead run had already passed the dam, according to the agency's annual juvenile survival memo. Barging also stopped for 10 days in May due to high flows and a lock repair downstream at The Dalles, and fish collection at Little Goose had been suspended for a week while its powerhouse was being repaired.

NMFS scientists also said that juvenile survival of PIT-tagged salmon and steelhead through the hydro system was lower in 2011 than the previous two years, despite one of the highest flow regimes of the last 40 years. They said that juvenile yearling Chinook survival (hatchery and wild combined) from Lower Granite Dam to Bonneville Dam was nearly 52 percent--close to the long-term average, but lower than 2010's estimate of 59 percent and 2009's 55.5 percent.

NOAA's preliminary survival results for migration year 2011 showed that juvenile wild spring Chinook tagged above Lower Granite didn't really benefit from the barging strategy until after May 15, compared to bypassed smolts that were returned to the river, but smolts tagged at the dam and returned to the river showed better SARs throughout the migration season. However hatchery spring Chinook did not seem to benefit from barging in 2011. Both wild and hatchery steelhead showed a benefit from barging in 2011 through the entire season, with SARs about 50 percent better than inriver migrants.

For lower Columbia stocks that weren't barged, The CSS report showed that some SARs compared to overall SARs from the lower Snake. For spring Chinook smolts released from Carson Hatchery in 2011, the SAR was .32 percent (from Bonn. to Bonn.), while the SAR for Rapid River Hatchery springers transported from the lower Snake was .31 percent. The Rapid River inriver SAR for fish that passed eight dams as juveniles and eight more as adults was .23 percent. The Carson fish only had to pass one dam.

Other lower Columbia stocks exhibited higher SARs, according to the report, like Cle Elum hatchery spring Chinook at .91 percent (using McNary Dam as a starting point for juveniles and Bonneville as the finish line for adults) and wild spring Chinook from the John Day River (John Day Dam to Bonn.) that showed an estimated .82 percent SAR, which was much lower than the 4 percent to 6 percent SARs reported for the JD stock in other recent years.

The CSS report also noted that IDFG has calculated the SARS of run reconstructions from 1996 to 2010 and estimated survival about 35 percent higher than the CSS PIT tag results, which might be explained by counting errors at dams or tagging mortality.

Related Sites:
Latest results from the Fish Passage Center's ongoing Comparative Survival Study Fish Passage Center, 2013

Bill Rudolph
Despite High 2011 Flows, Spill, Barging Still Benefited some Stocks
NW Fishletter, January 9, 2014

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