*U.S. Dept Commerce/NOAA/NMFS/NWFSC/Publications*

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**NOAA F/NWC-187 - Status and Future of Spring Chinook Salmon in the Columbia River Basin—Conservation and Enhancement**

**STATUS OF SNAKE RIVER IDAHOSPRING CHINOOK SALMON STOCKS**

Dexter R. Pitman

**Idaho Department of Fish and Game**600 South Walnut StreetBoise, Idaho 83707

The status of spring chinook salmon originating above Lower Granite Dam and those stocks ofIdaho origin are examined. Abundance of adult salmon is compared to abundance just prior to and afterthe serious decline following completion of the mainstem Columbia and Snake River hydroelectricsystem in 1975 and to goals for run and stock restoration established in the aftermath.

Raymond (1979) documented the magnitude of the impact of the hydroelectric system on SnakeRiver spring chinook and noted with optimism that steps taken in 1975 to alleviate wine of the juvenilefish passage problems resulted in higher survival of smolts; and subsequent higher return of adults. Hefurther stated that with safe passage and guaranteed in-stream flows, upriver runs of salmon andsteelhead to the Snake River could be restored to former levels. Prior to hydroelectric system impacts,Snake River spring chinook salmon contributed to commercial, sport, and tribal fisheries in the ocean,Columbia River, and Snake River main stem and tributaries. Bjornn (1960) estimated that 45% of the443,000 spring and summer chinook entering the Columbia River on average each year from 1954 to1959 originated in Idaho. Horner and Bjornn, (1981) reported that, statewide, Idaho sport anglersharvested an, average of 23,000 spring and summer chinook annually prior to 1961 and the Ice HarborDam construction. By 1965, the first statewide salmon fishing closure occurred due to limitedescapement Tribal fisheries declined to limited areas and numbers. The Pacific Salmon Treaty andColumbia River Management Plan limited ocean and river catches of Columbia and Snake River springchinook to incidental harvest.

**Snake River Spring Chinook Run**

Chinook salmon counted annually at Ice Harbor and Lower Granite Dam before 11 June and17 June, respectively, are considered spring chinook. Sizes of spring chinook adult runs increasedduring the 1985-88 period to near the sizes of 1964-78 annual runs. A major decline occurred in1989.

The Snake River spring chinook run is comprised of various stocks. From the managementperspective of the Idaho Department of Fish and Game (IDFG), the spring chinook run may be dividedinto three major stock groups—hatchery stocks, natural stocks spawning naturally but influenced byhatchery production, and wild stocks.

**Hatchery Stocks**

Hatchery stock abundance has increased with hatchery construction and increased smoltproduction. Annual variation has occurred in adult returns from smolt releases. Without exception, adultreturns have not achieved the anticipated returns of mitigation planning. Returns have been an order ofmagnitude less than expected. In 4 of the 8 years since 1982, adult returns haw been lower than theadult brood requirement for hatchery smolt production.

These deficiencies have had biological and socioeconomic implications. Implementation of thenatural stock restoration program has been delayed by deficiency of brood fish. The high expectations of fishermen for hatchery-returning salmon have intensified conflicts between allocation and resource demands.

**Natural Stocks**

Natural stock abundance is indicated by long-term spawning redd counts in standard index areasof the Salmon River (White and Cochnauer 1989). Increases in redds from 1985 through 1987 werefollowed by decreases in 1988 and 1989. A rebuilding trend is not apparent.

The average redd count for the current 5-year period, 1984-88 (307 redds), was approximately13% of the pre-1969 5-year averaged redd counts. The current average is approximately 18% of theaveraged redd counts during the two 5-year periods from 1969 to 1978.

**Wild Stocks**

Wild spring chinook stock abundance is also monitored by a long-term Salmon River redd countindex program. The Salmon River redd count bottomed out in 1980 at 38 redds and then began agradual increase to 972 redds in 1988. Wild stocks declined in 1989 when less than 150 redds werecounted (IDFG preliminary data).

The average annual redd count for the 1984 through 1988 period was 28% of those countedon average during 5-year periods from 1959 to 1968. Redds counted during the low escapementsof 1979-83 averaged 8%. The 1989 redd count approximates that average.

**Discussion and Summary**

Raymond (1979) expressed optimism for spring chinook salmon stocks, but the status of Idahostocks has changed little. Juvenile passage and flow provisions have not allowed restoration of stocks toformer levels. Hatchery stocks are more abundant, but they are not replacing their predecessors atanticipated levels. To reach those levels of returning adult abundance given the smolt-to-adult returnsdemonstrated since 1980, either 10 times the number of smolts will need to be grown or their survivalrates must improve. It is doubtful whether a tenfold production increase is practical or realistic.

Natural stocks have not increased, but wild stocks have shown rebuilding. Dependency on thehatchery program for supplementation and interception of natural escapement to provide and supplement hatchery brood collection may be affecting natural stockstatus. The 1989 collapse of the Salmon River wild stock points out the tenuousness of itsrestoration.

Petrosky (IDFG unpubl. data 1989) estimated recruitment and percent smolt to adult returns (SAR)to two Idaho wild spring chinook tributaries for smolt migration years 1972-85. Recruitment of wildchinook ranged from 0.03 to 16.25 recruit redds per spawner redd. Recruitment was generally belowreplacement (1.0) when mean flow at Lower Granite Dam during molt migration was less than 85,000ft3/s. He estimated further by simulation modeling that SAR for a brood/smolt migration year iscorrelated positively with mainstem, flows during the smolt migration period (p < 0.001). At 85 kcfsminimum flow the predicted SAR was 0.36% compared to 1.28% at 115 kcfs. At 0.36%, SARspawning escapements are predicted not to be met. At 1.28%, SAR spawning escapement would bemet, and, in addition, a 50% terminal fishery harvest rate could occur. Coded-wire-tag returns from summer chinook hatchery stock at McCall Hatchery demonstrated SAR and flow relationship similar to the wild spring chinook analyses.

Provision of guaranteed and suitable flows during the juvenile migration period is the single mosteffective action capable of restoring hatchery, natural, and wild stocks of Idaho-origin spring chinooksalmon to productive status. Improved survival would bring actual adult returns closer to anticipatedreturns. In turn, supplementation life stages would be available for natural stock development. Improvedsurvival would minimize a future supplementation needs as selfsustaining natural production occurred.Finally, wild stock rebuilding would occur and be secure when faced with periodic environmental stress.Given healthy status of each stock group, management needs for resource management and fisheryallocation could be satisfied.

**References**

Bjornn, T. C. 1960. Salmon and steelhead in Idaho. Idaho Wildl. Rev. July-August,p. 12-13.

Horner, N., and T. C. Bjornn. 1981. Status of upper Columbia and Snake River spring chinooksalmon in relation to the Endangered Species Act. Univ. Idaho, Idaho Coop. Fish. Res. Unit.Moscow, Idaho. Rep. U.S. Fish Wildl. Serv.

Raymond, H. L. 1979. Effects of dams and impoundments on migrations of juvenile chinook salmonand steelhead from the Snake River, 1966 to 1975. Trans. Amer. Fish. Sm. 108(6):505-529.

White, M., and T. Cochnauer. 1989. Salmon spawning ground surveys. Idaho Dep. Fish Game,Fish. Res. Rep., 47 p. (Available from IDFG, 600 South Walnut Street, Boise, ID 83707.)

**QUESTIONS AND ANSWERS**
- Q:
- Regarding yaw observations on flow vs. percentage of adult return—are the wild smolts in the river from 15 April to 15 May during periods of Water Budget flows?

- A.
- We do not know, but we are interested in PIT-tag studies to show exactly what stocks are in-river at what times, and what a water budget of 5 or 9 days, for example, would accomplish. Wecould see how water is used and try to provide minimum needed flows for 80% of the years, tokeep the appropriate genetic integrity of stocks. Also keep in mind that when we report totalredd counts of 134, for example, we often found only one or two redds in the transects—there isnot much to work with.

- Q:
- Dr. Bjornn did not show a good relationship of survival to flow. You emphasized flows as the majorfactor to improve the lot of wild fish during outmigration, while Dr. Bjornn suggested moretransportation—how do you reconcile the differences?

- A:
- I don't know if I can—one needs to compare the 15 April-15 May dates in the two sets of data andlack at the flow vs. transport program. One saw 95% losses at the Lower Granite forebay in 1977and 1987; they never arrived at the collector dam to benefit by transportation.

- Q:
- What program does Idaho envision for irrigation and hydropower to deal with the needed flows?

- A:
- We are trying to muster interest and hope that we am not forgotten out there. Idaho has a significantportion of the potential production area—5,000 miles of pristine environment. We just need to getback sufficient broodstocks. Fish have equal status with flood control and power—the general publichas to be aware of the problems.

- Q:
- NMFSs PIT-tagged wild fish outmigrated in late May—would you move the water budget to later,and also release hatchery fish later?

- A:
- We want to accomplish this, and it is the direction we are going. There is a social element for thereasons. We cannot ignore the hatchery fish; however, if it came down to protecting the wild fish, wewould do that. Our priority is first the resource, then the allocation.

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