Course:CONS200/2023WT2/Impacts of hydro dams on Pacific salmon populations

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Pacific salmon in the Pacific Northwest are a significant marine species, regarded for their ecosystem, commercial, and cultural values. Salmon migrate from freshwater to the ocean to spend their adulthood, before returning back upstream to spawn at their natal locations. Historical and emerging research show that salmon populations may be significantly impacted by the construction of hydroelectric dams along their natural habitats. Implications discussed in this article include chemical changes in the water, physical barriers, evolutionary and genetic implications, habitat degradation and spread of non-native species, and delayed mortality. These effects are mediated by current remedial actions such as fish ladders and hatcheries. Discourse on the future of hydro dams and conservation include cultural responses, dam removal efforts, and future recourse.

Background

Species of Pacific Coast Salmon: King (Chinook), Chum, Coho, Pink, and Sockeye.

Pacific salmon populations

Five major Pacific salmon species make up over 9000 different populations in the Northern Pacific region: Chinook (Oncorhynchus tshawytscha), Chum (Oncorhynchus keta), Coho (Oncorhynchus kisutch) Pink (Oncorhynchus gorbuscha), and Sockeye (Oncorhynchus nerka). Salmon exhibit anadromous behaviour, meaning that they hatch in freshwater, spend their adult lives in the ocean, and migrate back to their natal streams nearing the end of their life cycle to lay eggs and die.[1]

The migratory routes of salmon are crucial for the ecosystem; as salmon move to different places throughout their lifespan, they interact with other aquatic species and carry nutrients to fertilise surrounding habitats. Depending on the species, their routes can vary from a few hundred kilometres to over thousands of kilometres across the entire Pacific Ocean.[1][2] The average age of maturity for Pacific salmon is just under four years, with a range of two to seven years.[3] From small ponds and streams to large lakes, estuaries, rivers, and eventually the ocean, salmon migrations encompass a significant variety of aquatic habitats.

Approximately 127 species directly and indirectly rely on salmon in the food chain.[1] Due to their interconnectedness with other species and their habitats, the tracking of salmon populations is often helpful in estimating general ecosystem health.[1] The life systems salmon are interconnected with are greatly affected by hydro dams, which pose a variety of barriers to salmon migration.

Conservation status

Out of the five major Pacific salmon species, the International Union for Conservation of Nature (IUCN) has only assessed sockeye salmon populations on a global scale. The reported global status for sockeye salmon is "least concern (LC)".[4]

COSEWIC conservation statuses

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) has assessed Pacific salmon populations. The summary of their statuses is as follows:

  • Chinook: (12 populations assessed)[5]
    • not at risk: 1
    • special concern: 1
    • threatened: 3
    • endangered: 4
    • data deficient: 3
  • Chum: not yet assessed
  • Coho: (one population assessed)[6]
    • threatened: 1
  • Pink: not yet assessed
  • Sockeye: (seven populations assessed)[7]
    • special concern: 2
    • endangered: 2
    • extinct: 3

Hydroelectric dams

Hydroelectric dams (also referred to as hydro dams) are a significant source of electricity, irrigation, flood control, transportation, and recreation.[8][9] While dams are largely multipurpose, they are known for generating hydropower, a relatively clean and renewable source of energy. Most hydro dams function by drawing energy from moving or falling water. Water is stored up and released to generate kinetic energy which can then be turned into electricity.[10]

There are over 15,000 dams in Canada and 90,000 in the United States.[9][10] There is no comprehensive list of dams that impact Pacific salmon populations specifically. The most cited location in research pertaining to this topic is the Columbia River in British Columbia, Canada.

Hydroelectric "Revelstoke Dam" in British Columbia, Canada.

The Columbia Region of southeastern British Columbia stretches from the north of Revelstoke to the Canadian-U.S. border. There are a total of four major hydroelectric dams, seven smaller hydroelectric dams, and two storage dams operated by BC Hydro:[11]

Impact on salmon populations

Biological and chemical impacts

Reservoirs of the hydro dams have a direct effect on the water temperature, which indirectly affects the salmon-rearing habitat and survival rate. The reservoirs can extend the time that water remains in the system, in other words, the reservoirs reduce water mobility and amplify heat absorption from sunlight.[12] This can lead to a warmer spring and delay the cooling in autumn. More importantly, reservoirs can induce the vertical temperature difference, which influences the temperature conditions within fishways and fish ladders (the portions of fishways that increase in elevation) at hydro dams.[13] As a result of the temperature gradients that obstruct migration, the passage time of the adult salmon through the fish ladder will be increased.[13] 

The extra migration time can impact the health of salmon by potentially affecting the metabolic processes of both adults and juveniles, further making them vulnerable to disease.[13] Moreover, research has shown that the mortality rate of sockeye salmon will increase when the water temperature rises and reaches to their tolerance limits.[14] The high temperature creates favorable conditions for virulent and pathogenic parasites to infect salmon.[14] For example, a specialist parasite, Lepeophtheirus salmonis, can highly infect the Pacific juvenile salmon in high temperature and low salinity conditions.[15] The longer the migration time, the higher the probability of salmon being infected by parasites in the ocean, then carried to infect more individuals and impact salmon populations.

Hydro dams can result in more consumption of energy for adult salmon migrating upstream, which limits the energy used for spawning. When the adult salmon relocate upstream from the ocean to the spawning areas, they rely on the olfactory cues (a chemical signal that can be detected by an animal's sense of smell) they leave when juvenile during reproductive migrations.[16] However, the multiple artificial lakes or reservoirs that are created by the hydro dams spread the odour (smell) while flowing along the river channels.[16] The adult salmon will spend a long time and consume more energy searching for the odour and ensuring the right place for spawning when migrating upstream. This results in a lack of energy for spawning, which decreases the reproduction rate and salmon population.

Physical barriers

The hydro dam structures served as the obstruction between the spawning and rearing habitat and the ocean, which created the fragmentations along the fishway. These fragmented areas are often difficult to encompass the high-quality habitats that are needed for breeding, rearing, feeding, and wintering.[17]

The hydro dam systems can result in negative effects on the migration timing of the aquatic organisms.[18] In the life cycle of the salmon, the juvenile salmon need to migrate downstream to the ocean that supports them to grow up. The hydro dam structures take two weeks longer for the juvenile salmon to migrate downstream.[19] This might be due to the dramatic decreased water flow caused by the reservoirs of hydro dams during the juvenile migration period, which results in the delayed ocean entry of juveniles.[20] Early migration has a higher survival rate than late migration. For example, the Chinook in the Columbia River has the highest juvenile-to-adult survival rate when migrating downstream in early to mid-May, whereas the survival rate has a dramatic drop down in early June.[21]

Evolutionary and genetic implications

The genetic structure of salmon can be influenced by both biological characteristics and environmental changes. The introduction of hydro dams to native populations result in river fragmentation, in turn influencing how salmon navigate the area over many generations. Rivers that become dammed limit the accessibility of the route, discouraging salmon from migrating. This could lead to previously anadromous species becoming "resident", meaning that they do not leave their spawning habitat to migrate elsewhere at any point in their lives.[17][22]

Resident populations tend to experience negative genetic effects, especially over multiple generations. This is a result of reduced population size, lower growth rates, and abnormal population dynamics, which lead to a decrease in genetic diversity and an increase in the risk of local extinction.[17]

Lower quality and limited areas for breeding in rivers and streams affected by river fragmentation also have detrimental effects on genetic deterioration.[17] For instance, dammed-off resident populations are suspect to inbreeding and physical deformities and are more likely to be threatened by extinction in the wild.[17]

Dams and other environmental barriers increase the likelihood of fish populations becoming resident, but the ability of salmon to adapt to a fragmented environment varies greatly in comparison to other fish populations.[17]

Columbia River from the Rowena Crest Viewpoint

Habitat degradation and spread of non-native species

Hydro dams can create new habitats for other species due to different water temperature and turbidity in fragmented areas. Such habitats have the potential to attract non-native fish species, further affecting salmon populations. Along the mainstems of the Columbia and Snake River, juvenile or adult salmon can consistently meet around 20-40 non-native species, especially in the reservoirs.[23] Moreover, non-native species are also found broadly in the tributaries of the Columbia River, which provide rearing and spawning habitats.[23]

Non-native species can function as both the predators and competitors in the marine food web. The presence of non-native species can threaten the salmon populations by limiting the food sources through competition and predating juvenile salmon.[23] In ocean conditions that have more turbidity and more predators, the large turbid plume can provide visual covers that protect the salmon from predators.[20] However, the river conditions that are characterized by low turbidity have facilitated the negative effects, which may result in the decreased population of salmon.

The introduction of non-native species that indirectly caused by hydro dams system can facilitate transmission of disease and hybridize with native species.[23]

Delayed mortality

There is limited research on the effects of hydro dams on delayed mortality (i.e., salmon dying at a later point in time after passing through a hydro dam, potentially due to the impacts of stress from crossing the hydro dam). While it has been assumed from past analyses that river fragmentation has significant impacts on salmon mortality, so much so that billions of dollars have gone into dam improvement,[24] comparison of smolt-to-adult-return rates (SARs) of different populations questions the true effect of hydro dams on delayed mortality. Previous literature describes mixed results on the interaction between having to cross multiple dams on smolt mortality. For instance, Chinook salmon migrating through eight dams in the Snake River and Columbia River hydro system actually have higher survival rates (i.e., 50%) than Chinook migrating through the Fraser River, which has no dams.[24] Counterintuitively, the overall SARs of the Snake River Chinook are drastically low (i.e., 1.1%), meaning that a mere one in 50 smolts survive to return as adults post-migration.[24] In comparison, a previous study measured SARs in the Yakima River population, which only migrates through four dams and has triple the survival rate of the Snake River population.[25]

Rechisky et al. (2013)[24] refute the hypothesis that hydro dams lead to significantly delayed mortality in the Snake River populations studied within the early stages of crossing the dams (i.e., five to six weeks). Potential research for the future is suggested to address the possibility of an even further delay in dam-induced mortality or the effects of unmonitored ocean life during maturity.

Current remedial actions

A variety of strategies are being implemented to address this issue.

Fish ladder in Issaquah, United States.

Fish ladders

Dams, while providing humans with hydroelectricity, can block the migratory practices of pacific salmon. Fish ladders are a method of allowing fish to pass through dams that they otherwise are not able to travel through because of the dam. Fish ladders, also referred to as fishways or fish passages, have a few key components to their design. For each step of the fish ladder, you must provide many things. Fish ladders need to have a small elevation drop between steps, keep a constant and consistent water depth, allow for areas that fish can rest between steps, have fast currents and slow, and finally be in a spot that is easily found and accessible by the fish that need to use it.[26] This last point is the biggest flaw; despite many studies finding success,[27] many highlight an issue with salmon being able to find the fish ladder.[28] If salmon could better find the fish ladders, their effectiveness would improve greatly.[28] One benefit that makes fish ladders more effective is that pacific salmon have strong swimming abilities and exceptional navigational skills which makes them more successful in using fish ladders than other species.[29]

Hatcheries

In an effort to combat declining salmon spawning rates across the Pacific Northwest, hatcheries have been opened to help bolster Pacific salmon populations.[30] One study showed that hatcheries can be effective at combating the trend of Pacific salmon returning to spawn at younger ages and smaller sizes by altering when salmon from the hatchery is released.[30] By decreasing connectivity of species and blocking access to spawning locations, hydro dams continue to encourage premature and irregular migration patterns.[31] Hatcheries are able to combat this issue by releasing salmon into streams and areas once swam in by salmon below or above impassable barriers.[31] This will lead to populations having new locations for spawning and rearing; with juveniles being released downstream of a dam, they are able to avoid barriers such as dams entirely.[31] The timing of the release of the salmon smolts will also affect the effectiveness of hatcheries and survivability of the salmon.[32] Hatcheries can time the release of salmon smolts at the right times of year to maximize their chances of survival by maximizing beneficial environmental conditions and minimizing the chances of dying to predators.[32]

Limitations

One issue with hatchery salmon is that they are associated with a higher rate of straying than naturally spawned salmon.[31] This can be a problem if straying hatchery salmon genes start mixing with naturally spawning salmon as this can alter the genetic fitness of the wild salmon population.[33] Thus, it is important for hatcheries to take proactive measures to try and mitigate the likelihood of straying to preserve wild salmon stock genetics.[33] Hatchery-born salmon have different survival rates than naturally spawned salmon.[34] These differences are not necessarily worse than naturally spawned salmon, only different. The hatchery salmon released into the Grande Ronde River basin were found to have a better chance of survival in the upper reaches of the river, while the naturally spawned salmon found it easier to navigate and survive the lower reaches.[34] These differences are the result of physiological differences in the salmon, with larger smolts demonstrating higher chances of survival than smaller smolts[34] – something for hatcheries to consider when releasing salmon.

As discussed previously, fish ladders are effective but only when fish can find the fish ladder.[28] If salmon are unable to do so, the implementation of fish ladders does not mean much. Furthermore, if poorly designed, fish can potentially get trapped in the fish ladder, further reducing their efficacy.[27] This issue is called “fish traps”.[27] For Yukon River salmon, fish would get stuck in a viewing chamber along the fish ladder which hindered their chance of making it through.[27] On top of looking for solutions to make it easier for salmon to find fish ladders, solutions must also be made to ensure fish do not get trapped along the fish ladder itself for positive results. Designs for fish ladders also cannot be reused from different areas as different designs can be more or less effective with different salmon species.[29] Different combinations of designs need to be considered to maximize its effectiveness with all fish species needing to use the fish ladder.[29] Pool and Weir designed fish ladders for example have been proven effective for Pacific salmon species, however, they have not demonstrated the same effectiveness for other non salmon species.[29]

Another issue not previously discussed for fish ladders is the potential for non-native fish species to use them to travel further up rivers that otherwise would have been blocked by dams.

The path forward

Assessing the future of hydroelectric dams in the Pacific Northwest and their impact on salmon populations remains a rapidly changing interdisciplinary pursuit. Numerous groups, both official and otherwise, continue to advocate for the preservation of salmon habitats. This advocacy extends into political, legal, social, academic, economic, and scientific spheres, and promotes a myriad of goals such as the destruction of existing dams, the discontinuation of proposed dam projects, the eventual restoration of rivers to their natural, unrestricted states, and the implementation of newer technologies such as fish ladders, hatcheries, pressurized propulsion systems, and temporary and permanent fish passage facilities.

Cultural Responses

Voices in support of and opposition to hydro dam projects come from across the political and geographic spectrums. In the Pacific Northwest, a significant portion of protest against damming is currently enacted by Indigenous and environmental groups, often working in tandem with each other to accomplish goals of natural stream flow and species restoration.

Support of hydro dams comes from a multitude of perspectives, including civilians, organizations, and governments, and exists for a variety of reasons, both economic and social.

Dam Removal Efforts

Klamath Basin Tribes and allies from the commercial fishing and conservation organizations stage a rally at Hydrovision 2006. The Tribes are calling for the removal of four Klamath River dams to help restore Klamath Salmon runs

Klamath River Dam Removal Project

The Klamath River basin in Oregon, USA, is comprised of 12,000 square miles of significant waterway and adjacent fluvial landscape. The river sits on the traditional territory of multiple Indigenous groups, many of which have relied on sustenance from the natural resources provided by the Klamath for centuries, but also runs through a number of urban and vacation communities that use the river for recreation, power, water sourcing, and transport.

Damming of the Klamath River began in the early 20th century, altering the flow of the river and disrupting the previous path of Pacific salmon.[35] Due to recent protest, environmental studies, and the fulfilment of contracts, the United States government announced that four dams along the river would be removed starting in 2023. The project will be the largest dam removal in history. The Department of Interior (DOI) estimates that the dam removal will free up 420 miles of salmon spawning habitat as well as improve water quality.[35]

Legal Recourse

Federal and regional governments in Canada and the United States currently have many legal protections in place for Pacific Salmon populations, however many of these policies are outdated and have proven to be ineffective over time. Revision of these laws can use a significant amount of time and resources, and can be even more difficult to effectively implement in practice. Regulations also exist for the construction and function of dams in general, although the impact of dams on Pacific salmon populations has not always been taken seriously by hydroelectric projects and certain project management gaps can exist that further impact salmon in negative ways. In both countries, legal action continues to exist as one of the most effective combatants of hydro dam disruption, and groups such as Indigenous nations, environmental organizations, and communities that rely on salmon fishing often pursue legal justice as one pathway to success.

A pair of Coho salmon, one species listed as threatened under the Species at Risk Act (SARA)

Canada

Many Canadian laws function to protect Pacific salmon, most notable the Fisheries Act and the Species at Risk Act (SARA). The Fisheries Act gives power to the Federal Ministry of Fisheries and Oceans to regulate activity that may harm fish habitats, including dams. Depending on the threat level to salmon as determined by the Ministry, the Act allows for the denial of project proposals on the basis of habitat damage.[36] As the threat of dams continues to become relevant, the Fisheries Act will remain an essential piece of legislation in the protection of Canadian Pacific Salmon. SARA, which is targeted at the preservation of wildlife in Canada, also seeks to protect and recuperate salmon populations as they face endangerment.[37] SARA lists a number of Pacific salmon species, namely coho, chinook, and sockeye, as particularly vulnerable.[37] Using the designations made under SARA, future amendments to Canadian laws as well as new conservation-forward proposals will be able to soundly and succinctly argue for the protection of crucial salmon habitats.

United States

Major pieces of legislation in the United States currently regulate how salmon populations are assessed, managed, and monitored. The Endangered Species Act (ESA) is a federal regulation of the identification and management of endangered species in the United States.[38] Among many other species, the ESA structures how salmon are managed, based on their endangerment status and population dispersion.[38] Under this Act, the risks that Pacific salmon face are calculated based on factors such as habitat fragmentation, river alteration, and barriers to migration, all of which are significantly impacted by the existence of dams, although the seriousness of dams as threats to salmon has come forward as a concern more recently.[38] The ESA requires the consultation of wildlife experts on state matters involving endangered species, meaning ongoing adjustments are constantly being made to the Act as experts learn more about the response of Pacific salmon to various environmental changes.[38] Recent amendments to the ESA have improved the conservation of native fish species by improving access to participation in voluntary conservation programs, which focus on community-based conservation measures as a part of President Joe Biden's nationwide goal to conserve at least 30% of the United States’ land and water by the year 2030. [39] As more evidence is collected regarding the impact of dams on American salmon, the ESA is likely to be amended to include the recommendations of conservation professionals. The National Environmental Policy Act (NEPA) also functions to protect wildlife in the U.S., requiring federal agencies to consider the environmental impact of proposed actions, including the construction and operation of dams.[40] Although NEPA only requires the consideration of species rather than their promotion above profit, it is due to pieces of legislation like NEPA that projects with devastating impact on salmon populations, like the initial Klamath river dams, are highly unlikely to be permitted in the future.[40]

The Pacific Salmon Treaty (PST) is a co-national treaty signed by Canada and the U.S. designed to prevent overfishing and ensure that Pacific salmon thrive to the level of optimum production.[41] While the goal of the treaty is primarily economic, it also highlights the importance of Pacific salmon to the citizens of both nations. The PST provides a stable legal framework for international negotiation surrounding the protection, conservation and freedom of movement of Pacific salmon populations, and is likely to form the basis of joint management of salmon movement in the future as the two nations mitigate the risks posed to these shared species.[41] The Treaty is amended every ten years to allow for relevant updates, including those related to conservation and dam impact. The next revision will occur in 2028.[41]

Conclusion

The Pacific salmon of the Pacific Northwest stand as keystone marine species, holding significant ecological, commercial, and cultural significance, but their existence faces substantial threats, particularly from the construction of hydroelectric dams. These dams impose multifaceted challenges to salmon populations, affecting their migratory patterns, genetic diversity, habitat quality, and overall survival. From altering water temperatures to creating physical barriers and facilitating the spread of non-native species, these structures disrupt the ecosystem upon which salmon depend. The resulting consequences, including delayed mortality and genetic implications, underscore the urgent need for comprehensive conservation efforts. Despite the severity of these challenges, various remedial actions are being undertaken. Fish ladders and hatcheries offer promising strategies to mitigate the effects of dams on salmon migration and reproduction. However, these solutions are not without their limitations, including issues of effectiveness and potential ecological repercussions such as genetic contamination from hatchery populations. The discourse surrounding the future of hydro dams and salmon conservation is complex and multifaceted. Efforts to address these challenges must be interdisciplinary, encompassing political, legal, social, economic, and scientific perspectives. Advocacy for the preservation of salmon habitats, alongside initiatives for dam removal and the implementation of alternative technologies, remains crucial for ensuring the long-term sustainability of Pacific salmon populations. Cultural responses also play a significant role in shaping the trajectory of salmon conservation efforts. Indigenous and environmental groups, alongside governmental and non-governmental organizations, continue to advocate for the protection and restoration of salmon habitats, highlighting the intrinsic value of these species to both natural ecosystems and human societies.

The future of Pacific salmon in the Pacific Northwest is linked to our collective commitment to conservation and sustainability. By addressing the complex challenges posed by hydroelectric dams and implementing comprehensive conservation strategies, we can strive towards a future where salmon thrive in their natural habitats, enriching both ecosystems and communities for generations to come.

References

  1. ↑ 1.0 1.1 1.2 1.3 Pacific Wild. (2023, September 28). Pacific Salmon Species Spotlight. https://pacificwild.org/pacific-salmon-species-spotlight/#:~:text=There%20are%20five%20major%20salmon,and%20Coho%20(Oncorhynchus%20kisutch).
  2. ↑ Government of Canada. (2019, December 9). Information about Pacific Salmon. https://www.pac.dfo-mpo.gc.ca/fm-gp/salmon-saumon/facts-infos-eng.html
  3. ↑ Government of Canada. (2023, November 7). Identify your catch. https://www.pac.dfo-mpo.gc.ca/fm-gp/rec/identify-identifier-eng.html#salmon
  4. ↑ IUCN. (n.d.). Sockeye salmon (Oncorhynchus nerka). IUCN Red List. https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.iucnredlist.org/species/pdf/4086387/attachment%23:~:text%3DFor%2520our%2520global%2520population%2520assessment,list%2520them%2520as%2520Data%2520Deficient.&ved=2ahUKEwir7J3606mFAxV8JDQIHRMADJ4QFnoECA8QAw&usg=AOvVaw08zPwHH3qwYDEJ0qDt2V8u
  5. ↑ "Chinook Salmon (Oncorhynchus tshawytscha): COSEWIC assessment and status report 2020". Government of Canada. 2020. Retrieved April 4, 2024.
  6. ↑ "Coho salmon (Oncorhynchus kisutch) interior Fraser population: COSEWIC assessment and status report 2016". Government of Canada. 2016. Retrieved April 4, 2024.
  7. ↑ "Sockeye Salmon (Oncorhynchus nerka): COSEWIC assessment and status report Fraser River Drainage Basin Canada 2021". Government of Canada. 2021. Retrieved April 4, 2024.
  8. ↑ Rechisky, E. L., Welch, D. W., Porter, A. D., Jacobs-Scott, M. C., & Winchell, P. M. (2013). Influence of multiple dam passage on survival of juvenile chinook salmon in the columbia river estuary and coastal ocean. Proceedings of the National Academy of Sciences - PNAS, 110(17), 6883-6888. https://doi.org/10.1073/pnas.1219910110
  9. ↑ 9.0 9.1 "Dams in Canada". Canadian Dam Association (CDA). n.d. Retrieved March 7, 2024.
  10. ↑ 10.0 10.1 "Types of Hydropower Plants". Department of Energy (.gov). n.d. Retrieved March 7, 2024.
  11. ↑ "Columbia Region". BC Hydro. n.d. Retrieved March 7, 2024. |first= missing |last= (help)
  12. ↑ Quinn, Thomas P.; Hodgson, Sayre; Peven, Charles (June 1997). "Temperature, flow, and the migration of adult sockeye salmon (Oncorhynchus nerka) in the Columbia River". Canadian Journal of Fisheries and Aquatic Sciences. 54: 1349–1360.
  13. ↑ 13.0 13.1 13.2 Caudill, C.C.; Keefer, M.L.; Clabough, T.S.; Naughton, G.P.; Burke, C.A.; Peery, Christopher (December 31, 2013). "Indirect Effects of Impoundment on Migrating Fish: Temperature Gradients in Fish Ladders Slow Dam Passage by Adult Chinook Salmon and Steelhead". PloS one. 8.
  14. ↑ 14.0 14.1 Keefer, M.L.; Peery, C.A.; Heinrich, M.J. (September 17, 2007). "Temperature-mediated en route migration mortality and travel rates of endangered Snake River sockeye salmon". Ecology of Freshwater Fish. 17: 136–145.
  15. ↑ Brookson, C.B.; Krkošek, M.; Hunt, B.P.V.; Johnson, B.T.; Rogers, L.A; Godwin, Sean. C. (September 2020). "Differential infestation of juvenile Pacific salmon by parasitic sea lice in British Columbia, Canada". Canadian Journal of Fisheries and Aquatic Sciences. 77: 1960–1968.
  16. ↑ 16.0 16.1 Drenner, S.M.; Harrower, W.L.; Casselman, M.T.; Bett, N.N.; Bass, A.L.; Middleton, C.T.; Hinch, S.G. (November 2018). "Whole-river manipulation of olfactory cues affects upstream migration of sockeye salmon". Fisheries Management and Ecology. 25: 488–500 – via WILEY.
  17. ↑ 17.0 17.1 17.2 17.3 17.4 17.5 Morita, Kentaro; Morita, S.H.; Yamamoto, Shoichiro (January 20, 2009). "Effects of habitat fragmentation by damming on salmonid fishes: lessons from white-spotted charr in Japan". Ecol Res. 24: 711–722.
  18. ↑ Nilsson, Christer; Reidy, Catherine A.; Dynesius, Mats; Revenga, Carmen (April 15, 2005). "Fragmentation and Flow Regulation of the World's Large River Systems". Science. 308: 405–408.
  19. ↑ Raymond, H.L. (November 1979). <505:eodaio>2.0.co;2 "Effects of dams and impoundments on juvenile chinook salmon and steelhead from the Snake River, 1966 to 1975". Transactions of the American Fisheries Society. 108: 505–529 – via ProQuest.
  20. ↑ 20.0 20.1 Muir, W.D.; Williams, J.G. (November 2012). "Improving connectivity between freshwater and marine environments for salmon migrating through the lower snake and columbia river hydropower system". Ecological Engineering. 48: 19–24.
  21. ↑ Scheuerell, M.D.; Zabel, R.W.; Sandford, B.P. (2009). "Relating Juvenile Migration Timing and Survival to Adulthood in Two Species of Threatened Pacific Salmon (Oncorhynchus spp.)". Journal of Applied Ecology. 46: 983–990.
  22. ↑ Samarasin, P., Shuter, B. J., & Rodd, F. H. (2017). After 100 years: Hydroelectric dam-induced life-history divergence and population genetic changes in sockeye salmon (oncorhynchus nerka). Conservation Genetics, 18(6), 1449-1462. https://doi.org/10.1007/s10592-017-0992-0
  23. ↑ 23.0 23.1 23.2 23.3 Waples, R.S.; Zabel, R.W.; Scheuerell, M.D.; Sanderson, B.L. (October 1, 2007). "Evolutionary responses by native species to major anthropogenic changes to their ecosystems: Pacific salmon in the Columbia River Hydropower System". Molecular Ecology. 17: 84–96.
  24. ↑ 24.0 24.1 24.2 24.3 Rechisky, E. L., Welch, D. W., Porter, A. D., Jacobs-Scott, M. C., & Winchell, P. M. (2013). Influence of multiple dam passage on survival of juvenile chinook salmon in the columbia river estuary and coastal ocean. Proceedings of the National Academy of Sciences - PNAS, 110(17), 6883-6888. https://doi.org/10.1073/pnas.1219910110
  25. ↑ Tuomikoski, J., McCann, J., Berggren, T., Schaller, H., Wilson, P., Haeseker, S., ... & DeHart, M. (2009). Comparative survival study (CSS) of PIT-tagged Spring/Summer Chinook and Summer Steelhead 2009 Annual Report. Comparative Survival Study Oversight Committee and Fish Passage Center. Prepared for Bonneville Power Administration, Portland, Oregon.
  26. ↑ Nakamura, F., & Komiyama, E. (2010). challenge to dam improvement for the protection of both salmon and human livelihood in shiretoko, japan's third natural heritage site. Landscape and Ecological Engineering, 6(1), 143-152. https://doi.org/10.1007/s11355-009-0083-6
  27. ↑ 27.0 27.1 27.2 27.3 Twardek, W. M., Cooke, S. J., & Lapointe, N. W. R. (2023). Fishway performance of adult chinook salmon completing one of the world's longest inland salmon migrations to the upper yukon river. Ecological Engineering, 187, 106846. https://doi.org/10.1016/j.ecoleng.2022.106846
  28. ↑ 28.0 28.1 28.2 Gutfreund, C., Makrakis, S., Castro-Santos, T., Celestino, L. F., Dias, J. H. P., & Makrakis, M. C. (2018). Effectiveness of a fish ladder for two neotropical migratory species in the paraná river. Marine and Freshwater Research, 69(12), 1848. https://doi.org/10.1071/MF18129
  29. ↑ 29.0 29.1 29.2 29.3 Keefer, M. L., Jepson, M. A., Clabough, T. S., & Caudill, C. C. (2021). Technical fishway passage structures provide high passage efficiency and effective passage for adult pacific salmonids at eight large dams. PloS One, 16(9), e0256805-e0256805. https://doi.org/10.1371/journal.pone.0256805
  30. ↑ 30.0 30.1 Bosch, W. J., Pandit, S. N., Sandford, B. P., Temple, G. M., Johnston, M. V., & Larsen, D. A. (2023). Effects of volitional emigration timing and smolt size on survival and age-at-return in a pacific salmon hatchery population. Environmental Biology of Fishes, 106(5), 1037-1059. https://doi.org/10.1007/s10641-023-01395-0
  31. ↑ 31.0 31.1 31.2 31.3 Fullerton, A. H., Lindley, S. T., Pass, G. R., Feist, B. E., Steel, E. A., & McElhany, P. (2011). Human influence on the spatial structure of threatened pacific salmon metapopulations: Human influence on salmon spatial structure. Conservation Biology, 25(5), 932-944. https://doi.org/10.1111/j.1523-1739.2011.01718.x
  32. ↑ 32.0 32.1 Bosch, W. J., Pandit, S. N., Sandford, B. P., Temple, G. M., Johnston, M. V., & Larsen, D. A. (2023). Effects of volitional emigration timing and smolt size on survival and age-at-return in a pacific salmon hatchery population. Environmental Biology of Fishes, 106(5), 1037-1059. https://doi.org/10.1007/s10641-023-01395-0
  33. ↑ 33.0 33.1 Knudsen, E. E., Rand, P. S., Gorman, K. B., Bernard, D. R., & Templin, W. D. (2021). Hatchery‐Origin stray rates and total run characteristics for pink salmon and chum salmon returning to prince william sound, alaska, in 2013–2015. Marine and Coastal Fisheries, 13(1), 41-68. https://doi.org/10.1002/mcf2.10134
  34. ↑ 34.0 34.1 34.2 Monzyk, F. R., Jonasson, B. C., Hoffnagle, T. L., Keniry, P. J., Carmichael, R. W., & Cleary, P. J. (2009). Migration characteristics of hatchery and natural spring chinook salmon smolts from the grande ronde river basin, oregon, to lower granite dam on the snake river. Transactions of the American Fisheries Society (1900), 138(5), 1093-1108. https://doi.org/10.1577/T08-108.1
  35. ↑ 35.0 35.1 "Klamath River Dam Removal and Restoration". Congressional Research Service. March 3, 2022.
  36. ↑ Government of Canada (October 28, 2019). "Fisheries Act (R.S.C., 1985, c. F-14)".
  37. ↑ 37.0 37.1 Government of Canada (April 1, 2024). "Species at Risk Act (S.C. 2002, c. 29)".
  38. ↑ 38.0 38.1 38.2 38.3 United States Environmental Protection Agency (September 6, 2023). "Summary of the Endangered Species Act".
  39. ↑ Schuldheisz, Christine. "Interior Department Finalizes Action to Strengthen Endangered Species Act". U.S. Fish and Wildlife Service.
  40. ↑ 40.0 40.1 Environmental Protection Agency (October 5, 2023). "What is the National Environmental Policy Act?".
  41. ↑ 41.0 41.1 41.2 Pacific Salmon Commission. "The Pacific Salmon Treaty".


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