For a while, it was feared that the barging process would interfere with the homing instinct. But National Marine Fisheries Service researchers paid attention to this question “from the inception of their studies”.5 They found no evidence that transported fish lost the homing instinct, probably because the salmon had already migrated many miles in the river before being collected for transportation. In addition, the transportation barges constantly recirculate water while they are going downstream. If juvenile salmon do imprint on the chemical composition of the mainstem water, they can do so in the barges. By 1997, Idaho officials would privately admit "there is no evidence that fish are somehow losing their homing instinct from the barging process[, because d]am to spawning beds conversion rates are the same as they were before the barging process started".6
Because most of the fish marked for transportation research are hatchery fish, there have also been persistent suggestions that wild fish do not benefit as much from transportation as hatchery fish. But if you exclude all the hatchery fish from the calculations, the TBRs are even more positive.
Another well-promoted hypothesis is delayed mortality. No one can really can think of a good reason why transported salmon should die long after leaving the barges. One idea is that piping the salmon into the barges stresses the juveniles. Bert Bowler, an Idaho Department of Fish and Game biologist, has gone so far as to tell reporters that "the stress of the fish from splashing them into the barges is responsible for the decline in returning adults".7 This notion lacks any basis in fact.
In fact, tests show no difference in survival rates of marked groups of chinook salmon that are subjected to high stress before release and those that are not.8 Tests show no difference in swimming endurance of yearling chinook tested before and after barging.9 Other evidence suggests that any stress-caused reduction in ability to evade predators would disappear within an hour.10 And above all else, we know that transported juvenile salmon stay alive for hundreds of miles after they leave the barge at the same rates as untransported fish.
The Northwest Power Planning Council’s Independent Science Group has recently put forth a more sophisticated version of the “delayed mortality” theory. They point out that juvenile salmon “die at rates related to physical conditions existing during the time of emigration in the river” and that there is an “apparent dependence of the survivals of both transported and untransported juvenile salmon on conditions in the hydroelectric system”.11 For this reason, they claim (in a widely-quoted passage), that “transportation alone, as presently conceived and implemented, is unlikely to halt or prevent the continued decline and extirpation of listed species of salmon in the Snake River Basin”.12
The fallacy here is the “apparent dependence”. What they are really saying is that in dry years, when conditions are worse in the river, death rates seem to be higher in the ocean too. With blame-the-dams blinders on, conservation biologists assume that the higher death rate in the ocean is somehow related to passage through the river. The obvious countervailing hypothesis, that dry years on land are correlated with poorer conditions in the ocean, is ignored.
The Independent Science Group does acknowledge, in another section of its report, that
“during periods of warm ocean conditions and reduced flow of the California Current, freshwater habitat conditions may also decline due to reduced stream flows and increasing river temperatures in Western Oregon. These effects suggest a kind of ‘double jeopardy’ for salmon stocks . . .”13
It is precisely this “double jeopardy”, and other adverse effects on salmon, that has hidden the positive effects of the transportation program. Transportation can’t alone offset the effects of bad ocean and freshwater conditions, but nothing can. As National Marine Fisheries Service scientists John Williams and Gene Matthews have explained, “this unproven theory [of transportation failure] has turned to fact in the minds of many because data were incorrectly interpreted . . .”14
Because transportation speeds up the migration process, it puts fish into the estuary sooner than they would otherwise get there. This was long thought to offset migration delay from the dams. However, there is evidence that survival of later-transported fish is higher.15 This could be because it is better for fish to arrive later, or it could be because conditions in the river are less favorable later, killing off more of the control groups compared to transported fish.
Over the next few years, substantial additional data will become available to measure changes in salmon survival within the river at each project, and the survival of transported fish. We may well find a time, early in the year, when transportation does not help the fish. But the good news will be that that is because in-river conditions are so good.
5 ISG, Return to the River 327.
6 B. Rudolph, "Latest Survival Research Highlighted at IT Meeting", NW Fishletter, Nov. 11, 1997 (information attributed to "NMFS sources").
7 "Barging of salmon debated", Eugene Register Guard, Nov. 24, 1995, p. 8. To give Mr. Bowler the benefit of the doubt, there is some chance that the reporter misquoted him.
8 See ISG, Return to the River 304.
9 C. Schreck et al., “Evaluation of facilities for collection, bypass and transportation of outmigrating chinook salmon”, Draft Annual Report for U.S. Army Corps of Engineers by Oregon Coop. Fish. Res. Unit, OSU (1994).
10 D. Chapman & A. Giorgi, “Comments on NMFS Draft Biological Opinion on FCRPS Operations”, at 12.
11 ISG, Return to the River 328 (emphasis added).
13 Id. at 483 (citation omitted).
14 J. Williams, G. Matthews & J. Myers, “The Columbia River Hydropower System: Does It Limit Recovery of Spring/Summer Chinook Salmon?”, at 7; see also Memo, M. Schiewe to W. Stelle, Aug. 1, 1997, at 1 (dismissing several critiques of transportation as “unfounded” based on most recent data).
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