*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**

**EXPECTATIONS FOR SPRING CHINOOK SALMONPOPULATION RESPONSES TO HABITAT ENHANCEMENT PROJECTSIN NORTHEASTERN OREGON**

Richard W. Carmichael

Oregon Department of Fish and WildlifeBadgley Hall, Eastern Oregon State CollegeLa Grande, Oregon 97850

Extensive effort and large sums of money are being expended throughout the Columbia Basin to enhance spring chinook salmon (*Oncorhynchus tshawytscha*) habitat. Some misconceptions exist regarding the near-term natural production benefits that will result from habitat enhancement projects in subbasins of the Snake River.

The Grande Ronde Subbasin serves as a good example to examine the theoretical potential for increasing spring chinook salmon production with habitat enhancement. Historically this basin supported large runs of spring chinook salmon (Van Cleve and Ting 1960; Smith 1975). Although accurate estimates of spawning escapement are not available, escapement has been indexed annually since the 1940s by enumeration of redds. Peak escapement occurred in 1957 when an average of 21.1 redds/km were observed (Thompson and Haas 1960; Oregon Department of Fish and Wildlife 1964-86). Spawner escapement remained fairly stable from 1964 to 1973 (range 6.5-10.8 redds/km), well below the peak in 1957. Escapement declined sharply in 1974 and has remained severely depressed (Fig. 1). There have not been substantial reductions in spring chinook habitat quantity or quality since the mid-1950s, when production levels were high; therefore, the reduction in population numbers cannot be attributed to degradation in rearing and spawning habitat. Population decline has occurred primarily due to reduced smolt outmigrant survival caused by major flow and passage alterations in the Columbia and Snake Rivers.

The eight dams that exist between the Grande Ronde River and the ocean impose a major density-independent mortality that has caused a substantial reduction in recruits per spawner at all spawner abundances. When we examine Ricker-type hypothetical stock-recruitment curves (Ricker 1975), we would expect that, as the density-independent mortality rates increased with the construction of each dam, the stock-recruitment curve would shift downward (A toward C in Fig. 2) with the equilibrium population size decreasing correspondingly (Junge 1970). This type of population response was observed for John Day River spring chinook salmon. Lindsay et al. (1986) reported significant declines in recruit-per-spawner ratios as dams below the John Day River were completed. The recruit-per-spawner ratio at equal spawner abundance levels was significantly less for the 1970-79 broods than for the pre-1970 broods. These changes in the population dynamics were attributed to decreased smolt survival that resulted from completion of John Day Dam and expansion of The Dalles Dam powerhouse. Over the past 15 years, the spawner escapement in the Grande Ronde Basin has been so low that the spawning and rearing habitat has been underutilized. Because of low densities, the egg-to-smolt survival rates have been approaching the theoretical maximum for this basin, with little density-dependent survival effects.

There is some evidence that the freshwater habitat in the Grande Ronde Basin is not currently limiting production. A large part of the spring chinook habitat is in wilderness areas in the Minam and Wenaha Rivers (Carmichael et al. 1986). The habitat in these drainages is relatively pristine and the quality is far superior to habitat quality in other drainages throughout the basin, which has been degraded for many years by a variety of land use activities. If the freshwater habitat was limiting production, we would expect the streams in the wilderness areas to support higher chinook production levels than equal-size streams with degraded habitat. Higher spawner densities were observed in wilderness habitat from 1964 to 1973; however, since 1974, redd densities in the wilderness habitat have been consistently equal to redd densities in the degraded streams (Fig. 3).

The habitat enhancement work that is ongoing can be categorized into two general areas, stream channel morphology alteration and riparian habitat recovery. I am unaware of evidence that indicates significant habitat improvement benefits from physical alterations of channel morphology; however, improved riparian habitat does result in improved habitat quality and increased carrying capacity (Platts 1981; Bottom et al. 1985). Even though habitat quality will be improved in the Grande Ronde Basin through riparian habitat protection and enhancement programs, spring chinook natural production will not increase significantly as a result until natural spawning escapement increases substantially. Other species of anadromous and resident fishes may benefit from habitat enhancement.

It would be negligent and shortsighted to discontinue habitat protection and enhancement work because near-term benefits will not be realized. It is critical to protect and enhance habitat for the long-term benefits. Riparian habitat recovery will take many years for severely degraded streams. Any reductions in habitat quality could result in reduced freshwater survival and cause populations on the edge of extinction to become extinct. Work will continue in the Snake and Columbia Rivers to improve smolt survival, and with improved smolt survival the recruit per spawner ratios of these depressed populations will rebound. We must remain optimistic that the productivity of upriver spring chinook salmon populations will be restored and the habitat will be fully seeded in the future.

**References**

Bottom, D. L., P. S. Howell, and J. D. Rodgers. 1985. The effects of stream alterations on salmon and trout habitat in Oregon. Oregon Department of Fish and Wildlife, unpubl. manuscr., 70 p. (Available from Oregon Department of Fish and Wildlife, Badgley Hall, La Grande, OR 97850.).

Carmichael, R. W., R. Boyce, and J. Johnson. 1986. Grande Ronde River spring chinook production report (U.S. v. Oregon). Oregon Department of Fish and Wildlife, unpubl. manuscr., 36 p. (Available from Oregon Department of Fish and Wildlife, Badgley Hall, La Grande, OR 97850.)

Junge, C. O. 1970. The effect of superimposed mortalities on reproduction curves. Fish Commission of Oregon, Research Briefs 12(l):22-43.

Lindsay, R. B., W. J. Knox, M. W. Flesher, B. J. Smith, E. A. Olsen, and L. A. Lutz. 1986. Study of wild spring chinook salmon in the John Day River system. Report to Bonneville Power Administration, Contract DE-A179-83BP39796, 119 p. (Available from Bonneville Power Administration, P.O. Box 362, Portland, OR 97208.)

Oregon Department of Fish and Wildlife. 1964-86. Results of spring chinook salmon spawning ground surveys. (Available from Oregon Department of Fish and Wildlife, P.O. Box 59, Portland, OR 97207.)

Platts, W. S. 1981. Effects of livestock grazing. *In*W. R. Meehan (editor), Influence of forest and rangeland management on anadromous fish habitat in Western North America, Series 7. U.S. Forest Service, Pacific Northwest Forest and Range Experiment Station, General Technical Report PNW-124. (Available from U.S. Forest Service, 319 SW Pine, Portland, OR 97201.)

Ricker, W. E. 1975. Computation and interpretation of biological statistics of fish populations. Fish. Res. Board Can. Bull. 191:1-382.

Smith, A. K. 1975. Fish and wildlife resources of the Grande Ronde Basin, Oregon, and their water requirements. Project F-69-R-10, Completion Report. (Available from Oregon Department of Fish and Wildlife, P.O. Box 59, Portland, OR 97207.)

Thompson, R. N., and J. B. Haas. 1960. Environmental survey report pertaining to salmon and steelhead in certain rivers of eastern Oregon and the Willamette River and its tributaries. Part 1, 432 p. Fish Commission of Oregon.

Van Cleve, R., and R. Ting. 1960. The condition of salmon stocks in the John Day, Umatilla, Walla Walla, Grande Ronde, and Imnaha Rivers, 83 p. (Available from Oregon Department of Fish and Wildlife, P.O. Box 59, Portland, OR 97207.)

Figure 1. Spring chinook salmon redd counts in the Grande Ronde River Basin for the years 1964-86. Data points are 5-year averages.

Figure 2. Hypothetical Ricker-type stock recruitment curves.

Figure 3. Spring chinook salmon redd counts in wilderness streams and degraded streams in the Grande Ronde River Basin, 1964-86. Data points are 5-year averages.

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