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Environmental issues with salmon

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Environmental issues with salmon

Spawning sockeye salmon in Becharof Creek, Becharof Wilderness, Alaska

Salmon population levels are of concern in the Atlantic and in some parts of the Pacific. Alaska fishery stocks are still abundant, and catches have been on the rise in recent decades, after the state initiated limitations in 1972.[1][2] Some of the most important Alaskan salmon sustainable wild fisheries are located near the Kenai River, Copper River, and in Bristol Bay. Fish farming of Pacific salmon is outlawed in the United States Exclusive Economic Zone, however, there is a substantial network of publicly funded hatcheries,[3] and the State of Alaska's fisheries management system is viewed as a leader in the management of wild fish stocks. In Canada, returning Skeena River wild salmon support commercial, subsistence and recreational fisheries, as well as the area's diverse wildlife on the coast and around communities hundreds of miles inland in the watershed. The status of wild salmon in Washington is mixed. Out of 435 wild stocks of salmon and steelhead, only 187 of them were classified as healthy; 113 had an unknown status, 1 was extinct, 12 were in critical condition and 122 were experiencing depressed populations.[4]

Environmental pressures

All species of Pacific salmon (not including steelhead) die shortly after spawning. This one was photographed at a spawning site along Eagle Creek in Oregon.

The population of wild salmon declined markedly in recent decades, especially North Atlantic populations which spawn in the waters of western Europe and eastern Canada, and wild salmon in the Snake and Columbia River system in northwestern United States. The decline is attributed to the following factors:

  • Sea lice - transfer of parasites from open-net cage salmon farming, especially sea lice, has allegedly reduced numbers. The European Commission (2002) apparently concluded, "The reduction of wild salmonid abundance is also linked to other factors but there is more and more scientific evidence establishing a direct link between the number of lice-infested wild fish and the presence of cages in the same estuary.",[5] however it is impossible to very this statement from the reference provided It is reported that wild salmon on the west coast of Canada are being driven to extinction by sea lice from nearby salmon farms.[6] Unfortunately for Dr Krkosek and his research group their electronic modelling predictions of a collapsed salmon fishery have not eventuated, with two of the best runs ever recorded for wild salmon. This raises real questions over the validity of the models and their dire predictions. For Atlantic salmon smolts, it takes as few as eight sea lice to kill the fish. On the Pacific Coast where the smolt are much smaller, only one or two can be critical, often resulting in death. In the Atlantic, sea lice have been a proven factor in both Norwegian and Scottish salmon declines. In the Western Atlantic, there has been little research at sea, but sea lice numbers in the period after 2000 do not appear to be a significant factor in the critical decline of endangered inner Bay of Fundy salmon. The situation may have been different in the 1980s and 1990s, but we are unlikely ever to know the factual history in that regard.
  • Overfishing - in general, has reduced populations, especially commercial netting in the Faroes and Greenland. Several seafood sustainability guides have recommendations on which salmon fisheries are sustainable and which have negative impacts on salmon populations.
  • Warming in ocean and river water can delay spawning and accelerate the transition to smolting.
  • Ulcerative dermal necrosis - (UDN) infections of the 1970s and 1980s severely affected adult salmon in freshwater rivers.
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  • Habitat - the loss of suitable freshwater habitat, especially degradation of stream pools and reduction of suitable material for the excavation of redds has caused a reduction in spawning. Historically, stream pools were, to a large extent, created by beavers (see section below). With their extirpation, the nurturing function of these ponds was lost. Reduced retention of the nutrients brought by the returning adult salmon in stream pools has lowered populations. Without stream pools, dead adult salmon tend to be washed straight back down the streams and rivers, so the nutrients are not available for the hatchlings. The construction of dams, weirs, barriers and other "flood prevention" measures bring severe adverse impacts to river habitat and on the accessibility of those habitats to salmon, particularly in the northwest USA, where large numbers of dams have been built in many river systems, including over 400 in the Columbia River Basin.[7] Other environmental factors, such as light intensity, water flow, or change in temperature, dramatically affects salmon during their migration season.[8] Modern farming methods and various sources of pollution have resulted in loss of invertebrate diversity and population density in rivers, thus reducing food availability. Reduction in freshwater base flow in rivers and disruption of seasonal flows, because of diversions and extractions, hydroelectric power generation, irrigation schemes, barge transportation, and slackwater reservoirs, inhibit normal migratory processes and increase predation for salmon.[9] Agricultural practices, such as the removal of riparian plants, destabilization of stream banks by livestock and irrigation processes, result in a loss of suitable low-gradient stream habitats.[10][11]

Fishery pressures

A great threat to Pacific salmon conservation is commercial fishing. There are many methods of harvest for the commercial salmon fishing industry, such as trolling, seining, and gillnetting. Gillnets are an extremely size-selective method of harvest, where a long net is placed in the path of the salmon’s migration to their natal stream in hopes of entangling the salmon for commercial harvest. Fish too small to be caught pass through the net, fish too large cannot be entangled, only catching fish that fall somewhere in between. By selectively harvesting certain sizes of fish, governed by the mesh-size of the gillnet, some age-class and length-class fish are selectively removed from the population, progressively leaving phenotypically smaller spawners. Fecundity generally decreases with length. So, smaller fish produce fewer eggs than larger fish.[12] There is also concern regarding the genetic information passed down from the fish. If the majority of spawning fish in a particular salmon run has gotten smaller due to the size-selective fishing methods, the run could eventually evolve to become smaller.


Gillnets are designed to harvest a specific sized fish. For example, Washington Department of Fish and Wildlife's 2010 Commercial Regulations had a 7-inch (180 mm) minimum mesh size restriction for Chinook, and a 5-inch (130 mm) minimum – 5.5-inch (140 mm) maximum for sockeye.[13] Possible problems arising from this selective harvest are smaller reproducing adult fish, as well as the unexpected mortality of the fish which sustain injuries from the gillnet but are not retained in the fishery. Most salmon populations include several age classes, allowing for fish of different ages, and sizes, to reproduce with each other. A recent 2009 study looked at 59 years of catch and escapement data of Bristol Bay sockeye to determine age and size at maturity trends attributable to the selectivity of commercial gillnet harvests. The study found that the larger females (>550 mm) of all age classes were most susceptible to harvest.[12] The study suggests that smaller, younger fish were more likely to successfully traverse the gillnet fishery and reproduce than the larger fish. The study also found that the average length of sockeye harvested from 1946–2005 was 8 mm larger than the sockeye who escaped the gillnet fishery to spawn, reducing the fecundity of the average female by 5%, or 104 eggs.[12]

If a salmon enters a gillnet, but manages to escape, it often sustains injuries. These injuries can lead to a lower degree of reproductive success. A study aimed at quantifying mortality of Bristol Bay sockeye salmon due to gillnet-related injuries found that 11 - 29% of sockeye sustained fishery-related injuries attributable to gillnets, 51% of those fish were expected to not reproduce.[14]

North America

The Columbia River salmon population is now less than 3% of what it was when Lewis and Clark arrived at the river.[15] Salmon canneries established by settlers beginning in 1866 had a strong negative impact on the salmon population. In his 1908 State of the Union address, U.S. President Theodore Roosevelt observed that the fisheries were in significant decline:[16][17]

The salmon fisheries of the Columbia River are now but a fraction of what they were twenty—five years ago, and what they would be now if the United States Government had taken complete charge of them by intervening between Oregon and Washington. During these twenty—five years the fishermen of each State have naturally tried to take all they could get, and the two legislatures have never been able to agree on joint action of any kind adequate in degree for the protection of the fisheries. At the moment the fishing on the Oregon side is practically closed, while there is no limit on the Washington side of any kind, and no one can tell what the courts will decide as to the very statutes under which this action and non—action result. Meanwhile very few salmon reach the spawning grounds, and probably four years hence the fisheries will amount to nothing; and this comes from a struggle between the associated, or gill—net, fishermen on the one hand, and the owners of the fishing wheels up the river.

The commercial salmon fisheries in California have been either severely curtailed or closed completely in recent years, due to critically low returns on the Klamath and or Sacramento Rivers, causing millions of dollars in losses to commercial fishermen.[18] Both Atlantic and Pacific salmon are popular sportfish.

Salmon populations now exist in all the Great Lakes. Coho stocks were planted in the late 1960s in response to the growing population of non-native alewife by the state of Michigan. Now Chinook (King), Atlantic, and Coho (silver) salmon are annually stocked in all Great Lakes by most bordering states and provinces. These populations are not self-sustaining and do not provide much in the way of a commercial fishery, but have led to the development of a thriving sportfishery.

Relief efforts

Several governments and nongovernmental organizations (NGOs) are sharing in research and habitat restoration efforts to relieve this situation.

  • In the western Atlantic, the Atlantic Salmon Federation has developed a major sonic tracking technology program to understand the high at-sea mortality since the early 1990s. Ocean arrays are deployed across the Baie des Chaleurs and between Newfoundland and Labrador at the Strait of Belle Isle. Salmon have now been tracked half way from rivers, such as the Restigouche, to Greenland feeding grounds. Now, the first line of the Ocean Tracking Network initiative is installed by DFO and Dalhousie University of Halifax, from Halifax to the edge of the continental shelf. First results include Atlantic salmon travelling from the Penobscot River in Maine, the "anchor river" for US Atlantic salmon populations.
  • In the northern Atlantic, the North Atlantic Salmon Fund, led by Icelandic entrepreneur Orri Vigfússon, has worked closely since 1989 with governments and fishermen for conservation. The conservation efforts are not limited to oceans, and a sustainable angling scheme has been developed in rivers, notably in Vopnafjörður, Iceland.
  • Throughout the Pacific Rim, the Wild Salmon Center partners with communities, businesses, governments, and other non-profits to protect and preserve healthy salmon ecosystems and the biodiversity on which these ecosystems depend.

Results overall show estuary problems exist for some rivers, but issues involving feeding grounds at sea are impacting populations as well. In 2008, returns were markedly improved for Atlantic salmon on both sides of the Atlantic Ocean, but no one knows if this is a temporary improvement or sign of a trend.

In the Pacific Northwest, one of the most notable relief efforts is the Puget Sound Partnership.[20] The Puget Sound Partnership is currently working to implement policy change at the local level to alter the fate of salmon. Salmon recovery is guided by implementation of the Puget Sound Salmon Recovery Plan, adopted by the National Oceanic and Atmospheric Administration (NOAA) in January 2007. This recovery plan was developed by Shared Strategy, a grassroots collaborative effort to protect and restore salmon runs across Puget Sound. The Puget Sound Partnership has now rehabilitated over 800 acres of salmon habitat and it plans to continue to fight nearshore development and human impact affecting important salmon ecosystems. The Partnership's Action Agenda plans to instigate the Elwha Dam removal, begin restoration of the Nisqually Estuary and removal of derelict Fishing gear, and continue with the current salmon Recovery Plan. In order to ensure the future of Pacific Northwest salmon, the Partnership continues to encourage Stormwater & Low Impact Development, and advocates the "Puget Sound Starts Here" public education program.

Another notable local relief effort is the People for Puget Sound. People for Puget Sound is a citizen group founded by Kathy Fletcher in 1991 working to restore the health of our local land and waters with help from volunteers in the Puget Sound basin.[21]

Sweden will stop salmon fishing in Baltic Sea in 2013 to protect it.[22]


  1. ^ "1878–2010, Historical Commercial Salmon Catches and Exvessel Values".  
  2. ^ Viechnicki, Joe (2011-08-03). "Pink salmon numbers record setting in early season". KRBD Public Radio in Ketchikan, Alaska. Retrieved 6 August 2011. 
  3. ^|low fish returns in Southeast this summer have been tough on the region's hatcheries
  4. ^ (Johnson et al. 1997)
  5. ^ Scientific Evidence of Sea Lice from Fishfarms Seriously Harming Wild Stocks, .
  6. ^ "Martin Krkosek, Jennifer S. Ford, Alexandra Morton, Subhash Lele, Ransom A. Myers, and Mark A. Lewis Declining Wild Salmon Populations in Relation to Parasites from Farm Salmon. (14 December 2007) ''Science'' 318 (5857), 1772". 2007-12-14.  
  7. ^ Moscrip, A., Montgomery, D. "Urbanization, Flood Frequency, and Salmon Abundance in Puget Lowland Streams". JAWRA Journal of the American Water Resources Association.
  8. ^ "Aquaculture : Seasonal downstream movements of juvenile Atlantic salmon, Salmo salar L., with evidence of solitary migration of smolts". ScienceDirect. Retrieved 2010-03-18. 
  9. ^ Pacific States Marine Fisheries Commission "When Salmon Are Dammed". Pacific States Marine Fisheries Commission, 1997.
  10. ^ Bradford, MJ., Irvine, JR. "Land use, fishing, climate change, and the decline of Thompson River, British Columbia, coho salmon". Canadian Journal of Fisheries and Aquatic Sciences, 2000.
  11. ^ Orr, Raymond I. "Northwest Salmon Make Legal Headway." Indian Country Today
  12. ^ a b c Kendall, Neala W, Jeffery J. Hard and Thomas P. Quinn. 2009. Quantifying Six Decades of Fishery Selection for Size and Age at Maturity in Sockeye Salmon. Evolutionary Applications. 523-536.
  13. ^ Washington Department of Fish and Wildlife. 2010 Puget Sound Commercial Salmon Regulations. .
  14. ^ Baker, Matthew R and Daniel E Schindler. 2009. Unaccounted Mortality in Salmon Fisheries: Non-retention in Gillnets and Effects on Estimates of Spawners. Journal of Applied Ecology (46). 752-761.
  15. ^ "Endangered Salmon". U.S. Congressman Jim McDermott. Archived from the original on 2006-11-15. Retrieved 2006-11-17. 
  16. ^ "Columbia River History: Commercial Fishing". Northwest Power and Conservation Council. 2010. Retrieved January 26, 2012. 
  17. ^ Theodore Roosevelt (December 8, 1908). "State of the Union Address Part II by Theodore Roosevelt". Retrieved 31 January 2012. 
  18. ^ Hackett, S., and D. Hansen. "Cost and Revenue Characteristics of the Salmon Fisheries in California and Oregon". Retrieved 2009-06-01. 
  19. ^ "Project Bear Lake". Retrieved 2007-02-03. 
  20. ^
  21. ^
  22. ^ Suomen Luonto 1/2012 (27.1.2012) page 10(Finnish)

Further reading

  • Atlas of Pacific Salmon, Xanthippe Augerot and the State of the Salmon Consortium, University of California Press, 2005, hardcover, 152 pages, ISBN 0-520-24504-0
  • Making Salmon: An Environmental History of the Northwest Fisheries Crisis, Joseph E. Taylor III, University of Washington Press, 1999, 488 pages, ISBN 0-295-98114-8
  • Trout and Salmon of North America, Robert J. Behnke, Illustrated by Joseph R. Tomelleri, The Free Press, 2002, hardcover, 359 pages, ISBN 0-7432-2220-2
  • Come back, salmon, By Molly Cone, Sierra Club Books, 48 pages, ISBN 0-87156-572-2 - A book for juveniles describes the restoration of 'Pigeon Creek'.
  • The salmon: their fight for survival, By Anthony Netboy, 1973, Houghton Mifflin Co., 613 pages, ISBN 0-395-14013-7
  • A River Lost, by Blaine Harden, 1996, WW Norton Co., 255 pages, ISBN 0-393-31690-4. (Historical view of the Columbia River system).
  • River of Life, Channel of Death, by Keith C. Peterson, 1995, Confluence Press, 306 pages, ISBN 978-0-87071-496-2. (Fish and dams on the Lower Snake river.)
  • Salmon, by Dr Peter Coates, 2006, ISBN 1-86189-295-0
  • Lackey, Robert T (2000) "Restoring Wild Salmon to the Pacific Northwest: Chasing an Illusion?" In: Patricia Koss and Mike Katz (Eds) What we don't know about Pacific Northwest fish runs: An inquiry into decision-making under uncertainty, Portland State University, Portland, Oregon. Pages 91–143.
  • NEWS January 31, 2007: U.S. Orders Modification of Klamath River - Dams Removal May Prove More Cost-Effective for allowing the passage of Salmon
  • Salmon age and sex composition and mean lengths for the Yukon River area, 2004 / by Shawna Karpovich and Larry DuBois. Hosted by Alaska State Publications Program.
  • Trading Tails: Linkages Between Russian Salmon Fisheries and East Asian Markets. Shelley Clarke. (November 2007). 120pp. ISBN 978-1-85850-230-4.
  • The Salmons Tale one of the twelve Ionan Tales by Jim MacCool
  • "Last Stand of the American Salmon," G. Bruce Knecht for Men's Journal
  • Sea Lice and Salmon: Elevating the dialogue on the farmed-wild salmon story Watershed Watch Salmon Society, 2004.

External links

  • , an NFB documentary on West Coast salmonPlea for the Wanderer
  • Fish farms drive wild salmon populations toward extinction Biology News Net. December 13, 2007.
  • Salmonid parasites University of St Andrews Marine Ecology Research Group.
  • Watershed Watch Salmon Society A British Columbia advocacy group for wild salmon
  • The Link Between Farmed Salmon, Sea Lice and Wild SalmonWild Salmon in Trouble: - Watershed Watch Salmon Society. Animated short video based on peer-reviewed scientific research, with subject background article Watching out for Wild Salmon.
  • The scientific case for changing salmon farmingAquacultural Revolution: - Watershed Watch Salmon Society. Short video documentary. Prominent scientists and First Nation representatives speak their minds about the salmon farming industry and the effects of sea lice infestations on wild salmon populations.
  • Genetic Status of Atlantic Salmon in Maine: Interim Report (2002) Online book
  • University of Washington Libraries Digital Collections – Salmon Collection A collection of documents describing salmon of the Pacific Northwest.
  • .. Canned Salmon Recipes by Alaska Packers' Association, 1900 e-book with color illustrations, available from Internet Archive
  • Salmon Recipes Collected recipes using Salmon at
  • Low Sodium Salmon Recipe Recipe to make smoked salmon mousse.
  • Salmon-omics: Effect of Pacific Decadal Oscillation on Alaskan Chinook Harvests and Market Price Kevin Ho, Columbia University, 2005.
  • Salmon Nation A movement to create a bioregional community, based on the historic spawning area of Pacific salmon (CA to AK).
  • spp.) in the Canadian Western Arctic, by S. A. StephensonOncorhynchusThe Distribution of Pacific Salmon (
  • Sea Lice - Coastal Alliance for Aquaculture Reform. An overview of farmed- to wild-salmon interactive effects.
  • Salmon Farming Problems - Coastal Alliance for Aquaculture Reform. An overview of environmental impacts of salmon farming.
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