North Atlantic Salmon conservation Organization | est 1983

Habitat Protection

Habitat Protection and Restoration

Over the last 150 years much salmon habitat has been lost and this must have been a major contributory factor to the decline in wild salmon stocks. Causes include visible factors, such as hydro-electric dams, and the invisible, but highly damaging, impacts of chemicals and nutrients from activities such as industrial and domestic waste discharges, agriculture, forestry and waste from fish farming. Many other activities and conditions may have negative physical, chemical or biological impacts on habitat.

In 2024, NASCO’s Parties agreed a new Ten-Year Strategy and Action Plan, including an objective to maintain and, where possible, increase the current productive capacity of salmon habitat. As part of its work towards achieving its Strategic Goal, ‘to prioritise and drive actions necessary to slow the decline of wild Atlantic salmon populations and demonstrate that restoration is possible’, in 2026 NASCO developed new Guidelines for the Protection, Restoration and Improvement of Atlantic Salmon Habitat.

While these Guidelines are not intended to be prescriptive, their purpose is:

  • to assist jurisdictions in making further progress in protecting, restoring and improving salmon habitat, subject to local legislative constraints;
  • to provide for an exchange of relevant information; and
  • to assist jurisdictions in the preparation of future Conservation Commitment Reports (CCRs) and Performance Indicators on habitat protection, restoration and improvement as well as the process for reviewing the CCRs.

While Atlantic salmon continue to face significant challenges, there are examples of habitat restoration and recovery efforts that demonstrate what positive steps can be made.

Habitat Restoration

Tree planting on the River Gairn in the upper Dee catchment (Scotland)

In response to recommendations from NASCO, the River Dee Trust and Fishery Board in Scotland has undertaken a range of habitat restoration work, including a programme of tree planting in areas of the upper Dee catchment. Planting trees can help fish in many ways: they provide shade, so lowering water temperatures; stabilise riverbanks and prevent erosion; improve the retention of rain water on land, so reducing flooding; help create new areas of habitat and input nutrients into the water by providing leaf litter and larger woody debris.

Clearing the Way

In the United States where the Penobscot River Restoration Project in Maine has brought dramatic change to the second largest river system in New England. A collaborative effort to balance fisheries restoration and hydropower production, the project included the removal of two dams that had blocked fish migrations for more than a century, and the construction of a river-like bypass around a third major dam that fish now use to access areas of habitat that are critical for their reproduction and recovery.

Before and after: the Veazie Dam was one of two major barriers removed as part of the Penobscot River Restoration Project in Maine

Water Quality

Water pollution is widely reported as one of the main causes of the decline in stocks of Atlantic salmon. In southern Norway, acidified rivers have been mitigated with lime to help improve water quality and restore fish populations. This direct local action is coupled with European nations making agreements to reduce atmospheric emissions of acidifying compounds. In Norway, a total of 23 acidified rivers that were virtually without salmon have been successfully restored through the National liming Programme. Between them, they now support fisheries with a catch in recent years of between 13,000 and 19,000 salmon. Each year, the Norwegian government spends more than €5 million for the liming programme. Recolonisation of salmon has taken place in a number of these rivers.

River restoration: limestone powder being dispensed via pipeline into Norway’s River Modalselva. The liming strategy has a special focus on water quality during the critical period in spring when young salmon change to smolts.

NASCO’s Resolutions, Agreements and Guidelines

Prior to 2024, progress in implementing NASCO’s Resolutions, Agreements and Guidelines has been assessed through the review of Implementation Plans and Annual Progress Reports.

Other NASCO Publications

References Related to Management of Atlantic Salmon Habitat

Click here to see references related to the protection, restoration and improvement of Atlantic salmon habitat.
  • Armstrong, J.B., Fullerton, A.H., Jordan, C.E., Ebersole, J.L., Bellmore, J.R., Arismendi, I., Penaluna, B.E. and Reeves, G.H. 2021. The importance of warm habitat to the growth regime of cold-water fishes. Nature Climate Change, 11, 354-361. https://doi.org/10.1038/s41558-021-00994-y
  • Bilby, R.E., Currens, K.P., Fresh, K.L., Booth, D.B., Fuerstenberg, R.R. and Lucchetti, G.L., 2024. Why aren’t Salmon responding to habitat restoration in the Pacific Northwest? Fisheries, 49, 16-27. https://doi.org/10.1002/fsh.10991
  • Bond, M.H., Nodine, T.G., Beechie, T.J. and Zabel, R.W. 2019. Estimating the benefits of widespread floodplain reconnection for Columbia River Chinook salmon. Canadian Journal of Fisheries and Aquatic Sciences, 76, 1212-1226. https://doi.org/10.1139/cjfas-2018-0108
  • Chittoor Viswanathan, V. and Schirmer, M. 2015. Water quality deterioration as a driver for river restoration: A review of case studies from Asia, Europe and North America. Environmental Earth Sciences, 74, 3145-3158. https://doi.org/10.1007/s12665-015-4353-3
  • Dugdale, S.J., Franssen, J., Corey, E., Bergeron, N.E., Lapointe, M. and Cunjak, R.A. 2016. Main stem movement of Atlantic salmon parr in response to high river temperature. Ecology of Freshwater Fish, 25, 429-445. https://doi.org/10.1111/eff.12224
  • Dugdale, S.J., Malcolm, I.A. and Hannah. D.M. 2024. Understanding the effects of spatially variable riparian tree planting strategies to target water temperature reductions in rivers. Journal of Hydrology 635: 131163. https://doi.org/10.1016/j.jhydrol.2024.131163
  • Ellings, C.S., et al. 2016. Changes in habitat availability for outmigrating juvenile salmon (Oncorhynchus spp.) following estuary restoration. Restoration Ecology, 24, 415-427. https://doi.org/10.1111/rec.12333
  • Fjeldstad, H.P., Barlaup, B.T., Stickler, M., Gabrielsen, S.E. and Alfredsen, K. 2012. Removal of weirs and the influence on physical habitat for salmonids in a Norwegian river. River research and applications, 28, 753-763. https://doi.org/10.1002/rra.1529
  • Fogel. C.B., Nicol, C.L., Jorgensen, J.C., Beechie, T.J., Timpane-Padgham, B., Kiffney, P., Seixas, G. and Winkowski, J. 2022. How riparian and floodplain restoration modify the effects of increasing temperature on adult salmon spawner abundance in the Chehalis River, WA. PLoS ONE 17, e0268813. https://doi.org/10.1371/journal.pone.0268813
  • Forestry Commission. 2019. Managing forest operations to protect the water environment. Forestry Commission Practice Guide. Forestry Commission, Edinburgh. 56pp. https://www.forestresearch.gov.uk/publications/managing-forest-operations-to-protect-the-water-environment/
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  • Garner, G., Malcolm, I.A., Sadler, J.P. and Hannah, D.M. 2017. The role of riparian vegetation density, channel orientation and water velocity in determining river temperature dynamics. Journal of Hydrology, 553, 471-485. https://doi.org/10.1016/j.jhydrol.2017.03.024
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  • Hendry, K., Cragg-Hine, D., O’Grady, M., Sambrook, H. and Stephen, A., 2003. Management of habitat for rehabilitation and enhancement of salmonid stocks. Fisheries Research, 62, 171-192. https://doi.org/10.1016/S0165-7836(02)00161-3
  • Hodgson EE, Wilson SM, Moore JW. 2019. Changing estuaries and impacts on juvenile salmon: A systematic review. Global Change Biology, 26, 1986–2001, https://doi.org/10.1111/gcb.14997
  • Imholt, C., Soulsby, C., Malcolm, I.A. and Gibbins, C.N., 2013. Influence of contrasting riparian forest cover on stream temperature dynamics in salmonid spawning and nursery streams. Ecohydrology, 6, 380-392. https://doi.org/10.1002/eco.1291
  • Isaak, D. J. et al. 2017. The NorWeST summer stream temperature model and scenarios for the western U.S.: A crowd-sourced database and new geospatial tools foster a user community and predict broad climate warming of rivers and streams. Water Resources Research, 53, 9181–9205. https://doi.org/10.1002/2017WR020969
  • Isaak, D.J., Luce, C.H., Horan, D.L., Chandler, G.L., Wollrab, S.P. and Nagel, D.E. 2018. Global warming of salmon and trout rivers in the Northwestern US: road to ruin or path through purgatory? Transactions of the American Fisheries Society, 147, 566-587. https://doi.org/10.1002/tafs.10059
  • Jackson, F.L., Fryer, R.J., Hannah, D.M., Millar, C.P. and Malcolm, I.A. 2018. A spatio-temporal statistical model of maximum daily river temperatures to inform the management of Scotland’s Atlantic salmon rivers under climate change. Science of the Total Environment, 612, 1543-1558. http://dx.doi.org/10.1016/j.scitotenv.2017.09.010
  • Jackson, F. L., Gilbey, J., Eagle, L.J.B., Fryer, R. J., and Malcolm, I. A. 2025. The status of juvenile Atlantic salmon and brown trout populations in Scotland’s rivers: The National Electrofishing Programme for Scotland (NEPS) 2023. Scottish Marine and Freshwater Science, 16, 107pp. https://doi.org/10.7489/12543-1
  • Jackson, F.L., Hannah, D.M., Ouellet, V. and Malcolm, I.A. 2021. A deterministic river temperature model to prioritize management of riparian woodlands to reduce summer maximum river temperatures. Hydrological Processes, 35, 14314.  https://doi.org/10.1002/hyp.14314
  • Jackson, F.L., Malcolm, I.A. and Hannah, D.M. 2016. A novel approach for designing large-scale river temperature monitoring networks. Hydrology Research, 47, 569-590. https://doi.org/10.2166/nh.2015.106
  • Jähnig, S.C., Lorenz, A.W., Hering, D., Antons, C., Sundermann, A., Jedicke, E. and Haase, P. 2011. River restoration success: a question of perception. Ecological Applications, 21, 2007-2015. https://doi.org/10.1890/10-0618.1
  • Justice, C., White, S.M., McCullough, D.A., Graves, D.S. and Blanchard, M.R. 2017. Can stream and riparian restoration offset climate change impacts to salmon populations? Journal of environmental management, 188, 212-227. http://dx.doi.org/10.1016/j.jenvman.2016.12.005
  • Kennedy, R.J., Johnston, P. and Allen, M. 2014. Assessment of a catchmentwide salmon habitat rehabilitation scheme on a drained river system in Northern Ireland. Fisheries Management and Ecology, 21, 275-287. https://doi.org/10.1111/fme.12077
  • Koed, A., Baktoft, H. and Bak, B.D. 2006. Causes of mortality of Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) smolts in a restored river and its estuary. River research and applications, 22, 69-78. https://doi.org/10.1002/rra.894
  • Koed, A., Birnie‐Gauvin, K., Sivebæk, F. and Aarestrup, K. 2020. From endangered to sustainable: Multi‐faceted management in rivers and coasts improves Atlantic salmon (Salmo salar) populations in Denmark. Fisheries Management and Ecology, 27, 64-76. https://doi.org/10.1111/fme.12385
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  • Lenane, R. 2016. Keeping Rivers Cool: A Guidance Manual. Creating riparian shade for climate change adaptation. Keeping Rivers Cool partnership initiative, 15pp. keeping-rivers-cool.pdf
  • Lennox, R.J., et al. 2021. The quest for successful Atlantic salmon restoration: perspectives, priorities, and maxims. ICES Journal of Marine Science, 78, 3479-3497. https://doi.org/10.1093/icesjms/fsab201
  • Louhi, P., Mäki‐Petäys, A. and Erkinaro, J. 2008. Spawning habitat of Atlantic salmon and brown trout: general criteria and intragravel factors. River research and applications, 24, 330-339. https://doi.org/10.1002/rra.1072
  • Malcolm, I.A., Millidine, K.J., Glover, R.S., Jackson, F.L., Millar, C.P. and Fryer, R.J. 2019. Development of a large-scale juvenile density model to inform the assessment and management of Atlantic salmon (Salmo salar) populations in Scotland. Ecological Indicators, 96, 303-316. https://doi.org/10.1016/j.ecolind.2018.09.005
  • Marsh, J.E., Lauridsen, R.B., Gregory, S.D., Beaumont, W.R., Scott, L.J., Kratina, P. and Jones, J.I. 2020. Above parr: Lowland river habitat characteristics associated with higher juvenile Atlantic salmon (Salmo salar) and brown trout (S. trutta) densities. Ecology of freshwater fish, 29, 542-556. https://doi.org/10.1111/eff.12529
  • Marttila, M., Louhi, P., Huusko, A., Vehanen, T., Mäki-Petäys, A., Erkinaro, J., Syrjänen, J.T. and Muotka, T. 2019. Synthesis of habitat restoration impacts on young-of-the-year salmonids in boreal rivers. Reviews in Fish Biology and Fisheries, 29, 513–527. https://doi.org/10.1007/s11160-019-09557-z
  • Mrozińska, N., Glińska-Lewczuk, K., Burandt, P., Kobus, S., Gotkiewicz, W., Szymańska, M., Bąkowska, M. and Obolewski, K. 2018. Water quality as an indicator of stream restoration effects—A case study of the Kwacza River restoration project. Water, 10, 1249. https://doi.org/10.3390/w10091249
  • Mundahl, N.D. 2025.Short-Term Response of Instream Habitats and Brown Trout (Salmo trutta) Populations to Habitat Rehabilitation in Two Trout Streams, Minnesota, USA. Fishes,  10, 14. https://doi.org/10.3390/fishes10010014
  • O’Connor, W.C.K. and Kennedy, R.J. 2002. A comparison of catchment based salmonid habitat survey techniques in three river systems in Northern Ireland. Fisheries Management and Ecology, 9, 149-161. https://doi.org/10.1016/j.ecolind.2018.09.005
  • Office for Environmental Protection. 2024. OEP report on the drivers and pressures affecting nature in Northern Ireland. Available at: https://www.theoep.org.uk/report/drivers-and-pressures-northern-ireland.
  • Pulg, U., Vollset, K.W. and Lennox, R.J. 2019. Linking habitat to density-dependent population regulation: How spawning gravel availability affects abundance of juvenile salmonids (Salmo trutta and Salmo salar) in small streams. Hydrobiologia, 841,13-29. https://doi.org/10.1007/s10750-019-03997-1
  • Pulg, U. et al. 2022. Long-term effects and cost-benefit analysis of eight spawning gravel augmentations for Atlantic salmon and Brown trout in Norway. Hydrobiologia, 849, 485-507. https://doi.org/10.1007/s10750-021-04646-2
  • Pulg, U. et al. 2024. Assessing the potential for gas supersaturation downstream of hydropower plants in Norway, Austria and Germany. Science of the Total Environment, 948, p.174645. https://doi.org/10.1016/j.scitotenv.2024.174645
  • Quilbé, R. et al. 2025 Cold-Water Thermal Refuge Enhancement and Creation for Salmonids: Successes, Failures, and Lessons Learned. River Research and Applications, 0, 1-28. https://doi.org/10.1002/rra.4462
  • Roni, P. and Beechie, T. 2013. Introduction to restoration: key steps for designing effective programs and projects. In Stream and watershed restoration, a guide to restoring riverine processes and habitats, First Edition, pp.1-11. P. Roni and T. Beechie (Eds). John Wiley & Sons, Ltd. https://doi.org/10.1002/9781118406618.ch1
  • Sinclair, J.S., Mademann, J.A., Haubrock, P.J. and Haase, P. 2023. Primarily neutral effects of river restoration on macroinvertebrates, macrophytes, and fishes after a decade of monitoring. Restoration Ecology, 31, e13840. https://doi.org/10.1111/rec.13840
  • Skoglund, H., Forseth, T. and Einum, S. 2024. Among‐river pattern in relative abundance of two salmonid fishes reflects temperature‐dependent competition. Freshwater Biology, 69, 1057-1068. https://doi.org/10.1111/fwb.14289
  • Smith, A.S. and Kurylyk, B.L. 2024. Pumping Groundwater to Create Cold-Water Thermal Refuges in Warming Rivers. Ecohydrology, 18, e2739. https://doi.org/10.1002/eco.2739
  • Soulsby, C., Malcolm, I.A. and Tetzlaff, D. 2024. JAMES BUTTLE REVIEW: Six decades of ecohydrological research connecting landscapes and riverscapes in the Girnock Burn, Scotland: Atlantic salmon population and habitat dynamics in a changing world. Hydrological Processes, 38, 15105. https://doi.org/10.1002/hyp.15105
  • Soulsby, C., Youngson, A. and Webb, J. 2024. The ecohydrology of rewilding: A pressing need for evidence in the restoration of upland Atlantic salmon streams. Hydrological Processes, 38, e15142. https://doi.org/10.1002/hyp.15142
  • Thompson, J., Pelc, C.E., Brogan III, W.R. and Jordan, T.E. 2018. The multiscale effects of stream restoration on water quality. Ecological Engineering, 124, 7-18. https://doi.org/10.1016/j.ecoleng.2018.09.016
  • Wegscheider, B., Linnansaari, T. and Curry, R.A. 2020. Mesohabitat modelling in fish ecology: A global synthesis. Fish and Fisheries, 21, 927-939. https://doi.org/10.1111/faf.12477
  • White, J.C., Khamis, K., Dugdale, S., Jackson, F.L., Malcolm, I.A., Krause, S. and Hannah, D.M. 2023. Drought impacts on river water temperature: A process‐based understanding from temperate climates. Hydrological Processes, 37, 14958. https://doi.org/10.1002/hyp.14958
  • Wilbur, N.M., O’Sullivan, A.M., MacQuarrie, K.T., Linnansaari, T. and Curry, R.A. 2020. Characterizing physical habitat preferences and thermal refuge occupancy of brook trout (Salvelinus fontinalis) and Atlantic salmon (Salmo salar) at high river temperatures. River Research and Applications, 36, 769-783. https://doi.org/10.1002/rra.3570
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