The Many Sources Aiding in the Decline of Wild Salmon Populations: Dams as the Main Contributors.
- Tree of Knowledge Research
- Feb 20, 2014
- 5 min read
<<This post is a continuation from previous discussions. To read the introduction, click here.>>
“The salmon runs of the Columbia River Basin were once so abundant that they were ‘nothing short of fabulous.’”[1] Many factors contribute to the decline of salmon populations, as this fish is sensitive to unique pressures that occur throughout their complex lifecycle. A reason for the drastic decline in different salmon populations is highly dependent on each stock’s particular ecosystem and thus is difficult to isolate. In order to formulate a holistic strategy for the recovery of these fish, however, one must understand the most prevalent sources of salmon decline. When looking to understand the sources of decline, one must view each factor comprehensively, not simply as an isolated issue. Some of the main contributors include overfishing, habitat destruction, hybridization with hatchery fish – thereby weakening the genetics of wild fish, and dam construction.
Beginning roughly in the mid to late 1800’s, the level of fishing for salmon in the Pacific Northwest increased due to the immigration of European settlers into the region.[2] During this same time period, technological advancement and large-scale adoption of efficient fishing methods such as gill nets, coupled with highly effective techniques to process, preserve, and transport catches made fishing for salmon much easier and more efficient.[3] Beginning with the twentieth century, many salmon stocks were reduced below sustainable levels. This fact puts the fishes’ capability of reproductive success at risk.[4]
Besides over-fishing, wild salmon have also been affected by the agriculture industry in the Pacific Northwest. Irrigation of crops is a necessity in the Pacific Northwest for farming; however, irrigation reduces water flows in river systems that salmon rely on for upstream travel and spawning.[5] In addition to the reduction of critical river flows, the agricultural use of chemical fertilizers and pesticides also has a negative impact on salmon runs.[6] Cattle grazing, for example, can lead to the degradation of water quality through increased sediment transport and physical alteration of spawning and nursery habitat.[7] The negative impacts from agriculture are further aggravated if a particular stock of salmon in a chosen drainage is already in decline.
A variety of other sectors of the U.S. economy affects salmon populations. For example, timber is a very valuable resource and thus invokes a strong interest to harvest. Timber harvesting modifies habitats, including salmon habitats.[8] Because salmon suffer from a degraded environment, their populations decline as timber harvesting continues. Logging and road construction has also caused an increase in the presence of sedimentation in tributaries that salmon rely on for spawning grounds.[9] Furthermore, logging has caused an increase in water temperature, which is not optimal for the fishes’ health.[10]
To add to the many evils that human society have bestowed on wild salmon populations, the implementation of fish hatcheries has caused unforeseen issues. To counteract the decline in wild salmon populations and still satisfy the demand for this “commodity” in the market, new technologies have been introduced to artificially spawn and raise Pacific salmon under laboratory conditions. [11] With the advent of this technology, fisheries managers focused on using hatcheries as a tool to maintain declining wild populations and offset the negative effects imposed by dams, habitat alterations, and the inevitable overexploitation of salmon populations by humans.[12] In certain cases, hatcheries were often successful in maintaining salmon runs that would not otherwise have survived.[13] Despite this feat, hatchery fish also create the problem of competition with wild species and the mixing of genetically isolated wild stocks.[14] This weakens the wild stock genetics, which attribute to accelerating the declines of wild salmon.[15] In addition, hatchery fish lead to management difficulties for maintaining runs of wild salmon by creating the illusion that salmon stocks are sufficiently populated by wild salmon when in reality, the salmon present in these stocks are a majority of hatchery-raised salmon.[16]
Despite the fact that wild salmon are one of the toughest species on the planet, over-fishing, pollution, and crossbreeding have taken a toll on wild salmon populations. Still, many point to the construction of dams as the key factor in preventing salmon populations from returning to historically sustainable, naturally thriving levels.[17] Dams exist on many rivers and tributaries in the Pacific Northwest, providing water for navigation, irrigation, power generation, log transport, and flood control.[18] Although dams were promised to be a better source of irrigation, water, electricity, and transportation, they in fact reduce the natural passage of spawning salmon and the travel of young fish to their journey toward the ocean.[19] Finding solutions to transporting salmon around dams has been challenge for fisheries managers and damn engineers. Dam engineers created fish “ladders” to allow fish to swim past them; however, salmon did not adapt well, especially as more and more dams were constructed.[20] If salmon could climb one dam, the need to climb 10 proved disheartening. Dam turbines killed many fish and those that could survive were poisoned by supersaturated oxygen levels injected by dam spill-wells.[21] Dams also alter several key characteristics of water including temperature, dissolved gases, sediment transport, and the quantity and timing of flow.[22] The implementation of each new dam caused negative consequences for wild salmon populations.
The diversity of these environmental impacts caused by dams complicates the recovery of salmon. Humanity has procured burdens through actions such as the harvest of salmon for economic purposes and the alteration of habitat for power production and water storage. Less direct impacts, which are usually wide-ranging spatially, such as agriculture and timber harvest, also contribute to the present decline of salmon. Still, the main driving force of salmon population decline is due to the continual construction and maintenance of dams. In the following section, this thesis will discuss in more detail a dam’s impact on salmon populations -- concentrating primarily on the Lower Columbia River as a case study.
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[1] Michael C. Blumm ; & Greg D. Corbin (FNd1), Salmon and the Endangered Species Act: Lessons from the Columbia Basin, 74 Wash. L. Rev. 519, 525 (1999).
[2] Brian R. Campbell, Casting A Net into Turbulent Waters: Indian Salmon Fishing Rights in Canada and the United States, 3 Hastings W.-N.W. J. Envtl. L. & Pol'y 101, 121 (1995).
[3] Findings relating to wild salmon and steelhead, Or. Rev. Stat. § 1-5.950.
[4] See Thomas C. Jensen, The United States-Canada Pacific Salmon Interception Treaty: An Historical and Legal Overview, 16 Envtl. L. 363, 369 (1986). at 372; Larry G. Rutter, Salmon Fisheries in the Pacific Northwest: How are Harvest Decisions Made?, in Pacific Salmon & Their Ecosystems 355, 356 (Deanna J. Stouder et al. eds., 1997) (discussing hatcheries, habitat, hydropower, and harvest as the main contributors to Pacific salmon decline).
[5] Marcel Aillery et al., Salmon Recovery in the Columbia River Basin: Analysis of Measures Affecting Agriculture, 14 Marine Resource Econ. 15, 26 (1999).
[6] Id.
[7] Id. at 28.
[8] Henry B. Lacey, Dancing in Place: The Clinton Administration and Aquatic Ecosystem Protection in the Pacific Northwest, 36 Nat. Resources J. 539, 559-60 (1996).
[9] Id. 563-64.
[10] Id.
[11] Amy L. Stein, State Fish Stocking Programs at Risk: Takings Under the Endangered Species Act, 20 Duke Envtl. L. & Pol'y F. 63 (2010).
[12] Id.
[13] Matthew Johnson, What Would the Salmon Say? An Argument for Supplementation to Help Rebuild Naturally Reproducing Salmon Populations in the Columbia Basin, 24 Pub. Land & Resources L. Rev. 45, 54 (2004).
[14] Id. at 58.
[15] Id. at 50.
[16] Id. at 55.
[17] See generally Michael C. Blumm, Sacrificing the Salmon: A Legal and Policy History of the Decline of Columbia River Salmon 279-308 (2002) (detailed discussion of the dam-breach issue).
[18] Lackey, supra, at § 5.
[19] Id.
[20] Michael T. Pyle, Beyond Fish Ladders: Dam Removal As A Strategy for Restoring America's Rivers, 14 Stan. Envtl. L.J. 97, 103-04 (1995).
[21] Id.
[22] Id.
