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Agencies, Tribes Release Chinook Smolt Survival Study by Bill Crampton Columbia Basin Bulletin - December 5, 2003

Columbia Basin fish and wildlife agencies and Tribes have released the 2002 Comparative Survival Study (CSS) which estimates survival rates for spring/summer chinook – both transported and in-river – from major hatcheries in the Snake River Basin and selected hatcheries from the lower Columbia River.

The study, funded by the Bonneville Power Administration through the Northwest Power and Conservation Council’s Fish and Wildlife Program, takes a look at Smolt-to-Adult Returns (SARs) from PIT-tagged spring/summer chinook for the migration years 1997-2000, and includes 2003 adult returns.

In the 100-page report, the CSS researchers conclude that SARs “of transported and in-river migrants were much less than the 2-6 percent SARs needed to recover Snake River spring/summer chinook.”

For 1997-2000, the SARs for wild chinook leaving Lower Granite Dam (LGR) as smolts and returning to Lower Granite as adults, were “mostly in the 1-2.5 percent range,” says the CSS study.

“The LGR-LGR SARs for hatchery chinook that outmigrated in 1997 to 2000 were very hatchery specific, being lowest for Dworshak and Lookingglass spring chinook hatcheries (mostly below 1.25 percent). SARs were similar between in-river and transported fish for Dworshak and Lookingglass hatcheries.

“Spring chinook from Rapid River Hatchery, and summer chinook from Imnaha and McCall hatcheries had SARs that increased yearly, reaching levels over 2 percent in most study categories in 1999 and 2000.

“Transported smolts had higher SARs for these latter three hatcheries than their in-river counterparts in most cases,” says the CSS study. “The highest SAR consistently occurred for McCall Hatchery summer chinook (the latest migrating stock). SARs of McCall Hatchery Smolts transported from Lower Granite Dam exceeded 4 percent in two years (1999 and 2000),” says the CSS study.

The CSS was prepared by the Fish Passage Center and Comparative Survival Study Oversight Committee: Thomas Berggren, Henry Franzoni and Larry Basham of the Fish Passage Center; Paul Wilson and Howard Schaller of the U.S. Fish and Wildlife Service; Charlie Petrosky of Idaho Fish and Game; Earl Weber of the Columbia River Inter-Tribal Fish Commission; Ron Boyce of Oregon Department of Fish and Wildlife; and Nick Bouwes of EcoLogical Research.

The objectives of the study include:

• development of a “long-term index” of transport SAR to in-river SAR for Snake River hatchery and wild spring/summer chinook smolts measured at Lower Granite Dam
• develop a long-term index of survival rates from release of smolts at Snake River hatcheries to return of adults to the hatcheries
• compare overall SARs for selected upriver and downriver spring/summer chinook hatchery and wild stocks
• begin a “time series” of SARs for use in hypothesis testing and long-term monitoring and evaluation

DeHart said the CSS study “has multiple applications,” noting that hatchery managers over time will get a better sense of what happens to the fish they release. She said they will be able to use SAR data for their own hatchery evaluations.

She said for Fiscal Year 2003, the CSS work cost about $800,000, with much of the money used for purchases of PIT-tags at $2.25 a piece.

One key fisheries agency, NOAA Fisheries, did not participate in the study or comment on the results.

John Ferguson, NOAA’s acting division director for the Fish Ecology Division of the Northwest Fisheries Science Center, said his agency, in preparation for the remand of the 2000 Biological Opinion for the federal hydropower system, is updating the analysis of SAR data and the effectiveness of the smolt transportation program.

He said NOAA’s updated smolt survival analysis will be presented to the region for review in the form of draft white papers in the coming months.

“We don’t have a comment on the CSS study,” Ferguson said. “We are focused on our own work, which will be forthcoming.”

The CSS study PIT-tagged and released annually more than 200,000 smolts from Snake River hatcheries (primarily Dworshak, McCall, Rapid River, and Imnaha) and 5,000-13,000 smolts from a downriver hatchery (Carson) in 1997-2000.

As for monitoring wild fish survival rates – in other words species listed under the Endangered Species Act – the study’s executive summary notes that the report “incorporates available wild chinook PIT tag data from smolt migration years 1994-2000 to estimate wild chinook SARs, to compare wild chinook SARs between transportation and in-river migration, and to compare wild and hatchery chinook responses to management actions.”

The study authors note that the CSS “increased PIT tag sample sizes of juvenile wild chinook for the 2002 and 2003 out-migrations (with plans to continue through 2004) to provide a comparison of SARs between transported and in-river wild Snake River migrants, as well as between Snake River and downriver wild stocks with similar life-history characteristics.”

In addition to the general SAR numbers cited above, the CSS findings to date include:

• Transportation benefits were more evident for summer chinook stocks than spring chinook stocks of Snake River hatchery chinook in 1997-2000.
• Little or no transport benefits were evident in most years for Snake River wild chinook based on available PIT tag data, 1994-2000.
• Delayed hydrosystem mortality was evident for transported Snake River hatchery chinook smolts, which died at a greater rate after release below Bonneville Dam than hatchery smolts that migrated through the hydrosystem in 1997-2000.
• Delayed hydrosystem mortality was evident for transported Snake River wild chinook smolts, which died at a greater rate after release below Bonneville Dam than wild smolts that migrated through the hydrosystem in 1994-2000.
• The CSS found evidence of delayed hydrosystem mortality of in-river migrants associated with collection and bypass at Snake River dams in 1997-2000 for hatchery chinook.
• The extent to which hatchery chinook can be used for a surrogate for wild chinook for survival over the different life stages is inconclusive from the 4 years of information where this comparison was possible.

Related Sites:
The full report is available at www.fpc.org/fpc_docs/CSS/final_2002_CSS_AnnualReport.pdf