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Latest Survival Data Good News for Barged Fish

by Bill Rudolph
NW Fishletter, January 19, 2012

Spring/summer hatchery chinook barged down the Snake River in 2009 had adult return rates ranging from 40 to 300 percent better than their inriver migrating counterparts, according to recent memos from the Fish Passage Center to some regional hatchery managers.

In recent years, barging has begun later because NMFS scientists saw patterns in survival data that showed early barged fish fared worse than fish that migrated inriver.

However, by barging later in the spring, some runs will likely get little benefit, since 50 percent of some stocks may be past collector dams by May 1, about the time barging starts. And increased levels of spill, in place since a 2006 court order, have reduced the number of smolts that are collected for barging at Lower Snake dams.

The FPC's Dec. 20, 2011 memo to the manager of Idaho's Sawtooth Hatchery says inriver migrating spring chinook from that facility had a 56-percent survival rate to below Bonneville Dam. But barged fish ultimately did much better, with the ratio of returning barged fish to inrivers (undetected at any Snake collector dams) pegged at 3.07. Only about 39 percent of the Sawtooth fish were barged.

Data for the 2010 Sawtooth outmigration is incomplete (jacks only, no adult data), but the memo reported that inriver juvenile survival was about the same (55 percent), and only 32 percent were barged. So far, the barged fish are returning at better than 2 to 1.

Rapid River Hatchery chinook showed return rates for fish barged in 2009 were also more than twice that of inrivers (2.04), with a SAR (smolt-to-adult return rate) of 1.29 percent compared to the inrivers' 0.63 percent. The FPC reported that about 44 percent of the RR fish were transported in 2009.

Hatchery fish from the McCall facility barged from the Snake in 2009 also showed benefits of nearly 2 to 1 over inriver migrators (1.94 ratio) with the transport SAR of 0.71 percent compared to the inrivers' 0.37 percent. Around 40 percent of the McCall fish were barged in 2009.

Clearwater Hatchery spring chinook showed a 41-percent benefit from barging in 2009, but only 25 percent were barged. These fish, along with chinook from the Dworshak Hatchery, reach collector dams earlier than most other stocks, since the facilities where they are raised are closer to the dams.

Dworshak spring chinook showed a 27-percent benefit from being barged in 2009, when about 34 percent were transported.

Summer chinook from the Pahsimeroi Hatchery showed a 79-percent benefit from barging in 2009, but only about 8 percent were barged that year.

Spring chinook from the Catherine Creek Acclimation Pond showed a 34-percent benefit from barging in 2009, with a 1.76-percent SAR compared to the inrivers' 1.3 percent. About 56 percent of those fish were barged, according to the FPC.

The 2009 hatchery springers from the Imnaha Acclimation Pond showed an 89-percent benefit from barging that year, with a 1.33-percent SAR compared to the inriver migrating SAR of 0.70 percent.

The final FPC 2011 CSS Report [Comparative Survival Study] released Nov. 30 estimated that transport SARS for wild Snake chinook in 2009 were almost exactly the same as for inriver migrants in 2009--1.01 percent.

That same report included an estimate of SARs for wild and hatchery steelhead that migrated in 2008, which found only a 12-percent benefit for barging wild steelhead that year. That was quite a drop from 2007's barging benefit of nearly three times over inriver migrators.

The FPC also said hatchery fish showed a 23-percent benefit from barging in 2008, down from 2007's 66 percent.

The return of the run at large could be higher than reported from the PIT-tagged hatchery and wild fish, since there is some evidence that PIT-tagged, clipped and coded-wire tagged hatchery spring chinook from the Yakima River returned at a rate about 25 percent lower than fish without the PIT tags.

Bill Rudolph
Latest Survival Data Good News for Barged Fish
NW Fishletter, January 19, 2012

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