CHAPTER 3: NATURAL FACTORS KILLING SALMON
“We will now discuss in a little more detail the struggle for existence.” Charles Darwin, On the Origin of Species
Most of the popular beliefs about salmon and the problems in their lives are the product of anthropomorphism and ignorance. Like every other species on earth, salmon are locked in a constant struggle for existence against other species, and homo sapiens is but one of many competitors.
Much salmon research since 1980 has focused on allocating blame for salmon declines. Nearly all of that research has been conducted by fishery agencies, which have a powerful vested interest in pointing the finger at causes of salmon decline that do not implicate their harvest management, and instead call for them to manage more and more salmon recovery programs. Blaming dams produces greater funding from dam revenues. After overfishing, however, natural salmon cycles are probably the most important factor in recent salmon declines. Nature, however, does not write checks to fishery managers. There is no money in blaming Nature.
While many scientific facts about salmon are subject to enormous dispute and obfuscation, practically everyone agrees that salmon are cold water fish, which will die if the water gets too warm. And practically everyone agrees that it is getting warmer in the Pacific Northwest.
I live in a rural community about 30 miles outside of Portland, and the old-timers in the vicinity will talk about how the Pudding River used to freeze in the winter, and there would be skating parties and sleigh rides. The Pudding River never freezes now. The mainstem Columbia River froze over in 1868. It hasn’t frozen over since then.
We have been measuring the temperature of the Columbia River since Bonneville Dam was built, and it has been rising steadily ever since we began measuring it. Here is a graph of the date every year when water temperature rises above 15.5 degrees Centigrade—about 60 degrees Fahrenheit.
Figure 4: Onset of Warm Columbia River Water Since 19381
Water temperatures have been rising above 60 degrees earlier and earlier in the year, to the point when there is now one full month less of cool water in the summer. Obviously, this is not going to work to the advantage of salmon that are in the river in the summertime.
Some blame dams for the warming trend, but the trend seems to have continued since 1975, even though no new dams have been constructed. The Northwest Power Planning Council staff concluded in 1986 that the “existing reservoir system has caused no significant change in the average annual temperature of the mainstem Columbia River”.2 In fact, the reservoirs have probably acted to dampen extreme swings in temperature. As the Council’s Independent Science Group observed in 1996, “[m]aximum temperatures in the mainstem Snake River, where salmon survival is most tenuous, are generally lower in summer than before the series of storage and mainstem reservoirs was installed. This is also true in the mainstem Columbia River.”3 No one has ever attempted to assess what positive effects on salmon, if any, would arise from flattening high temperature peaks.
Notwithstanding the scientific facts, most Northwest fishery agencies continue to assume that dams have raised river temperatures to the detriment of salmon. The official and contra-factual position of the National Marine Fisheries Service is that increased water temperatures, “a result of the impoundment of the river, have been shown to increase predation rates” on salmon.4 The Clinton/Gore Administration has even enlisted the United States Environmental Protection Agency to opine that dam alteration "may be the only alternative that meets the Clean Water Act" standards for water temperature.5 An EPA staffer, apparently thrilled to join the dam-bashing, gushed: "This is our coming-out party. We feel like debutantes."6
As scientific support for the idea that releasing water from upstream reservoirs will help salmon by making the river run faster has dwindled (the subject of Chapter 7), state and tribal fishery agencies have begun to agitate for reservoir releases to reduce temperatures, even raising the issue in court. But as the Independent Science Group recently pointed out, “[r]elease of deep, cold water from headwater storage reservoirs will not ameliorate high temperatures because the reservoirs are too far upstream”.7
Another piece of evidence that temperature may be critical results from comparing Upper Columbia stock declines to Snake River stock declines. The state and tribal-dominated “Plan for Analyzing and Testing Hypotheses” (PATH), an ongoing process that was supposed to instill “good science” into salmon decisionmaking, recently released preliminary conclusions. The state and tribal scientists are “reasonably confident” that upriver stocks have declined faster, which they blame on dam development. Yet they have “low confidence” that declines in upper Columbia stocks have correlated with increases in the number of dams.8 Water in the upper Columbia tends to be colder than water from the Snake, an effect apparently not considered as a root cause in salmon decline by the PATH researchers.
The warmer climate seems to have been loosely associated with lower rainfall in the Columbia River Basin. In recent years, salmon have been adversely affected by drought conditions. Such conditions have persisted in the Snake River Basin, in particular, during much of the 1980s and early 1990s.9 Low water conditions occurring during droughts destroy important spawning and rearing habitats for salmon. When salmon nests in shallow streams ("redds") become de-watered, eggs and pre-emergent fry perish.10 Droughts also can reduce overwintering survival of juvenile salmonids, and are usually associated with higher water temperatures in the summer.11 In addition, agricultural diversions often reduce flow to zero in drought years in streams that would otherwise constitute good habitat for juvenile salmon.
Scientists have considerable evidence about the long-term history of temperatures in the Pacific Northwest. James Chatters of the Pacific Northwest Laboratory and his colleagues have found that fossil remains tend to corroborate climate models suggesting that 6,000 to 7,000 years ago, the temperature in the Pacific Northwest was 2 degrees Celsius higher than at present. Analysis of archeological evidence suggests that salmon populations were anywhere from 30-60% below present populations.12 Thereafter, the climate became cooler, and salmon populations increased.
Dr. Chatters believes that the “little Ice Age” from 500 to 100 years ago may have represented the best conditions for salmon in the Pacific Northwest in thousands of years, and that efforts to restore salmon to that historic peak of abundance are unrealistic in the face of the warming trend since then. He thinks the late 1800s are “unrepresentative of the region’s long term productivity”.13
From a scientific perspective, it is entirely possible that the effect of rising water temperatures is larger than all the salmon mitigation measures that could be devised. No one has tried to figure out whether and to what extent all the efforts we undertake to recover salmon will make any difference in the face of rising temperatures. Generating electricity by burning fossil fuels instead of running hydropower plants—a major consequence of current salmon recovery efforts—is not likely to have a positive effect on the temperature problem.
In an era where most rivers in the Pacific Northwest never freeze over, longing for a return to 1850s salmon populations makes about as much sense as longing for a return of the Gold Rush. Trying to restore wild salmon populations to such historic levels makes no sense, unless we can somehow engineer salmon to survive in warmer climates.
NRC, Upstream at 196 (Prepub. ed.) (Figure 9-3).
2 “Compilation of Information on Salmon and Steelhead Losses in the Columbia River Basin”, at 147.
3 ISG, Return to the River at 166.
4 NMFS, Biological Opinion, “Reinitiation of the Consultation on 1994-98 Operation of the Federal Columbia River Power System and Juvenile Transportation Program in 1995 and Future Years”, Mar. 2, 1995, at 64.
5 Mary Lou Soscia, quoted in J. Brinckman, "EPA adds new twist to dispute on salmon", The Oregonian, Nov. 7, 1997, at B1.
7 ISG, Return to the River at 266.
8 Report in B. Rudolph, “PATH Researchers Report Preliminary Conclusions”, Clearing Up, Jan. 13, 1997, at 7.
9 Proposed Snake River Salmon Recovery Plan at II-25, 26.
12 J. Chatters, “A paleoscience approach to estimating the effects of global warming on salmonid fisheries of the Columbia River Basin”, reprinted in National Research Council of Canada, Symposium on Climate Change and Northern Fish Populations, at 489 (1992).
13 Quoted in B. Rudolph, “Archeologist Takes Long Look at Salmon Recovery”, Clearing Up, Jan. 20, 1997, at 7.
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