But for a time, in the near future, the numbers will greatly exceed the few million level. Salmon are members of complex marine communities and their population dynamics will be chaotic. Available habitat in Idaho, and predator prey relationships will take time to play out and settle into a somewhat steady population with ocean conditions playing a dominant role.
Return to the River, Independent Science Group (2000)
Prior to Euro-American development in the basin, the Columbia River may have supported more than 200 anadromous stocks, which returned 7 to 30 million adult salmon and steelhead to the river annually (Chapman 1986; NPPC 1986; Nehlsen et al. 1991).
. . .
Salmon have declined since the early 1980s from almost 2.5 million to less than 1 million returning adults, most of which (>80%) are now of hatchery origin. Wild fish abundance is approximately 1% of historical predevelopment abundance (National Research Council (NRC) 1996)
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In the lower Snake River analysis, they estimated that approximately 55 percent of the study area may have been suitable as fall chinook spawning habitat prior to hydroelectric development. Of particular interest was the river section between Little Goose and Lower Granite dams, in which 87 percent of the lineal river distance was predicted to be suitable fall chinook spawning habitat.
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One of the most interesting distribution patterns to emerge from recent surveys of the Columbia and Snake river mainstems, is the persistent use of tailwater areas below hydrosystem projects by fall chinook salmon as spawning areas (Garcia et al. 1994, Fish Passage Center website). Remnant fall chinook populations have been observed below nearly all projects in the mainstem Columbia and Snake rivers, attesting to the dispersal ability of fall chinook, as well as to their ability to find and colonize suitable available spawning habitats. We view this response by fall chinook in these habitats as testimonoy to the normative river concept we described in chapters 3 and 12 as a viable restoration strategy for increasing salmon abundance and productivity.
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Conclusions and Recommendations
Salmon restoration in the Columbia River is based on the prevailing belief that the primary problem for anadromous fish is mortality associated with juvenile passage through the mainstem dams and reservoirs.
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Although the Salmon comprises only 6% of the land area of the Columbia River Basin, it provides more anadromous spawning area than any other basin. The Salmon River produces 39% of the spring Chinook salmon, 45% of the summer Chinook salmon, and 25% of the summer steelhead returning to the mouth of the Columbia River.
Since the run timing is important for the Orca, Fall Chinook are considered separately from the Spring/Summer Chinook.
Compilation of Information on Salmon and Steelhead Losses in the Columbia River Basin -- Northwest Power Planning Council (March 1986)
Historic Abundance "The habitat-based estimate is based on extremely conservative data and the Pacific Fishery Management Council reports that it doesn't reflect a realistic run size. ... the range that is most reflective of the predevelopment run size is therefore about 8 to 16 million fish. Within this range, 10 to 16 million is probably the most reasonable... "
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From the beginning the Council has been aware that its judgment on goals likely would be a prudential judgment, not a judgment dictated by data. Reliable data are scarce for the predevelopment era. Although more recent data are plentiful, even very recent data may not be expressed in a way that enables comparative judgements (e.g., among fishing effort, timber harvest and trends in fish runs).
It is the Council staff's judgement, however, that the data must be taken as they are, and that further investment of time and effort scouring historical records is unjustified. The process of preparing this compilation has demonstrated to the Council staff that almost every facet of the data could be debated without end, yet further debate over the data would not achieve precision. The Council intends to make its prudential judgments taking those uncertainties into account.
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1.3 HABITAT LOSS AND DEGRADATION GENERALLY (Chapter 4)
There have been significant losses and degradation of salmon and steelhead habitat in the Columbia River Basin. Particularly severe was permanent blockage of habitat by large mainstem dams such as Chief Joseph and Grand Coulee dams and the Hells Canyon complex. The harmful effects fo such projects are irreversible because it is not feasible to provide fish passage facilities for them. Even if these areas were planted with non-native anadromous fish stocks, those stocks could not migrate and return to spawn. Even dams that permit fish passage (i.e. LSR dams) have inundated habitat destroying spawning and rearing areas and increasing downstream migration time. It is estimated that salmon and steelhead habitat in the entire basin has decreased from about 14,666 miles of stream before 1850 to 10,073 miles of stream persently, a 31 percent loss all due to water development. Salmon and steelhead habitat losses in the Columbia River above Bonneville Dam (including the Snake River) also has been intensive, decreasing from 11,741 miles of stream before 1850 to 7,582 miles of stream, about a 35 percent loss.
While the lower river area below Bonneville Dam has suffered significant losses of spring chinook habitat, there has been much less habitat loss compared to upriver areas. In the Willamette River, habitat has been opened to additional anadromous fish species (fall chinook, summer steelhead) due to the construction of the fishway at Willamette Falls. In the Columbia River system below Bonneville Dam, salmon and steelhead habitat has decreased from 2,925 miles of stream to 2,491 miles of stream, about a 15 percent loss.
Throughout the Columbia River Basin, additional salmon and steelhead habitat has been degraded by forest and farming practices, waste disposal, and other factors. In some areas such habitat degradation has been extensive; but its effects are largely reversible.
1.4 LOSSES OF UPRIVER FISH RUNS AND HABITAT (Chapter 5)
The greatest losses of fish runs and habitat have occurred in the upper Columbia and upper Snake areas. These losses are largely unmitigated. Three general factors are responsible for loss of upriver fish runs:
- Loss of habitat. See Section 1.3
- Passage mortalities at dams. Passage mortality is estimated at about 15 to 30 percent per dam for downstream migrants and 5 to 10 percent for upstream migrants. Cumulative passage mortality for untransported fish passing nine dams on the way to the ocean is approximately 77 to 96 percent.
- Mixed-stock ocean fishery. In a mixed-stock fishery, upriver and wild runs already weakened by habitat and passage losses, are fished at the same rate as lower river runs (heavily hatchery-supplemented). As a result weaker upriver runs may be overfished.
1.5 (Chapter 6) EFFECTS OF MITIGATION (Chapter 6)
Efforts have been made to mitigate the effects of development. Two of these efforts have had major implications for the salmon and steelhead fisheries. First was a series of fishing regulations that in addition to restraining harvest also contributed to a shift from inriver harvest to ocean harvest of some stocks. Columbia River chinook salmon caught in ocean fisheries (including Canada and Alaska) now account for about 73 percent of total harvest.
Second was the development of large-scale hatchery production of salmon and steelhead. In 1949, hatchery programs were developed under the Mitchell Act (16 U.S.C Sec 755). Most Mitchell Act hatchery fish are raised and released in the lower river, supporting the expansion of the lower river and ocean commercial fisheries. By the late 1960s, hatchery production of fall chinook and coho salmon and steelhead far surpassed natural production. Extensive production of hatchery fish has, along with permanent blockage by dams which eliminated some stocks, changed the genetic character (biological loss) of Columbia River Basin stocks. In addition, availability of large numbers of lower river hatchery fish causes overfishing of wild and upriver stocks in the mixed-stock harvest.
