Southern Resident killer whales heavily depend on Chinook salmon for their survival and Chinook are heavily dependent on healthy rivers. BC is in an unprecedented wild salmon crisis. While there are several key reasons for the predicament salmon face, one of these drivers includes the loss and destruction of freshwater habitat within their spawning watersheds.
In the US Pacific Northwest, the consequences for salmon from freshwater habitat loss have been well documented. But in BC, where high-quality studies on the biological consequences have been few and far between, this lack of evidence has contributed to the narrative that changes in the marine environment are the dominant driver of the low salmon survival now observed.
In 2021, a study by Kyle Wilson and his colleagues at Simon Fraser University found that logging strongly influenced the survival of three salmon species that required year-round freshwater habitat. Increases in the cumulative area logged were associated with a 97% or greater decline in freshwater productivity.
But logging is just step one in a series of sequential land use conversions that constitute ‘freshwater habitat loss’. Subsequent bulldozing, paving, and underground piping of water in a river basin trigger a cascade of effects that sever the structure, function, and processes of rivers that support salmon. They unravel the water quantity, quality, and physical attributes that nurture salmon through their most vulnerable life stages.
Habitat loss for salmon takes its greatest toll on the salmon species that rely on freshwater habitat year round. This reliance begins after fry emerge from their eggs in spring and continue to spend time (typically a year) feeding and growing before beginning their journey to the ocean the following year. The salmon species most often in need of year round habitat include coho, sockeye, steelhead, and Chinook salmon.
Habitat loss also includes alienation. Barriers such as dams prevent Chinook salmon from accessing large stretches of their spawning grounds, especially in the US. With fewer Chinook successfully spawning, hatching, and making it to the sea, Southern Resident killer whales lose a crucial food source.
In some places, fish passage systems such as fish ladders, trap-and-haul, and salmon cannons have been developed, but many dams are not equipped with these and they are not effective enough to mitigate the impacts of the barriers. Salmon hatcheries have also been used as a method to combat declining Chinook populations.
Hatchery-raised salmon often return smaller and younger than their wild counterparts. Hatchery salmon largely return in the fall, a time of year when salmon prey are most abundant. The spring and summer runs of Chinook are particularly important to Southern Resident killer whales. The glut of young hatchery salmon, suddenly released into the ocean, can also compete with wild salmon for food and resources. This ultimately harms wild Chinook and is not a solution for Southern Resident killer whales who need year-round access to large, old Chinook.
We created this map to emphasize the relationship between the recovery of Southern Resident killer whales and the recovery of wild Chinook salmon. We highlight barriers as only one habitat issue that Chinook salmon encounter while navigating to their natal rivers and the difficulty in just reaching their spawning grounds. We also suggest that critical habitat for Southern Residents should extend to the Chinook watersheds that supply their food.
Brooke Gerle, Misty MacDuffee. 2023. Chinook watersheds that feed into the critical habitat of Southern Resident killer whales. [web map]. Sidney (BC): Raincoast Conservation Foundation. www.raincoast.org/2023/03/mapping-chinook-watersheds-srkw/
About the map
Chinook distribution was determined through the use of multiple publicly available spatial data layers, research, and scientists’ knowledge. Layers were merged and modified to reflect major rivers that are believed to support Chinook salmon. Examples of large areas of historic habitat that have been restricted by dams were also included.
This map is not a complete display of Chinook distribution, as data limitations exist. We only included major anthropogenic barriers to fish passage for Chinook salmon. However, additional fish obstacle layers are included for British Columbia, Washington, Idaho, Oregon, and California that are not specific to Chinook salmon or Chinook habitat. The barriers are included to draw attention to the vast number of obstacles fish face while moving through their habitats.
Using the map
The widgets in the corners allow you to zoom in and out, zoom to your current location, search for an address or place, view the legend, change which layers are visible, and change the basemap. Watersheds and fish passage barriers will display more information when clicked on.
References and sources
Bureau of Land Management, Oregon State Office. 2022. BLM OR Fish Passage Barriers Point Hub. Distributed by Bureau of Land Management [cited 2023 Feb] from https://services1.arcgis.com/KbxwQRRfWyEYLgp4/arcgis/rest/services/BLM_OR_Fish_Passage_Barriers_Point_Hub/FeatureServer
California Department of Fish and Wildlife. 2021. California Fish Passage Assessment Database. Distributed by Biogeographic Information and Observation System [cited 2023 Feb] from https://services2.arcgis.com/Uq9r85Potqm3MfRV/arcgis/rest/services/biosds69_fmu/FeatureServer
Fisheries and Oceans Canada. 2016. Critical Habitat of Species at Risk. Distributed by Government of Canada Open Data [cited 2022 Nov] from https://open.canada.ca/data/en/dataset/db177a8c-5d7d-49eb-8290-31e6a45d786c. Contains information licensed under the Open Government Licence – Canada.
GeoBC Branch. 2003. BC Major Watersheds. Distributed by B.C. Data Catalogue [cited 2022 Nov] from https://catalogue.data.gov.bc.ca/dataset/bc-major-watersheds. Contains information licensed under the Open Government Licence – Canada.
GeoBC Branch. 2006. Freshwater Atlas Stream Network. Distributed by B.C. Data Catalogue [cited 2022 Nov] from www.catalogue.data.gov.bc.ca/dataset/freshwater-atlas-stream-network. Contains information licensed under the Open Government Licence – Canada.
Idaho Department of Fish and Game. 2019. Fish Barriers. Distributed by Idaho Department of Fish and Game [cited 2023 Feb] from https://gis.idfg.idaho.gov/server/rest/services/Fisheries/MapServer/0
Knowledge Management. 2007. Provincial Obstacles to Fish Passage. Distributed by B.C. Data Catalogue [cited 2023 Feb] from https://catalogue.data.gov.bc.ca/dataset/35bbac7c-2e2f-4587-9108-f4aa1e862809
National Hydrography. 2016. Watershed Boundary Dataset. Distributed by USGS – National Geospatial Technical Operations Center [cited 2022 Nov] from https://www.usgs.gov/national-hydrography/access-national-hydrography-products
NOAA National Centers for Environmental Information. 2021. Killer Whale (Southern Resident DPS). Distributed by NOAA Fisheries [cited 2022 Nov] from https://www.fisheries.noaa.gov/national/endangered-species-conservation/critical-habitat#:~:text=Critical%20habitat%20is%20defined%20as,management%20considerations%20or%20protection%3B%20and.
StreamNet, Pacific States Marine Fisheries Commission. 2019. Spring Chinook Distribution. Distributed by StreamNet [cited 2022 Nov] from https://www.streamnet.org/home/data-maps/gis-data-sets/
StreamNet, Pacific States Marine Fisheries Commission. 2019. Summer Chinook Distribution. Distributed by StreamNet [cited 2022 Nov] from https://www.streamnet.org/home/data-maps/gis-data-sets/
Washington Department of Fish and Wildlife Habitat Program, Fish Passage Division. 2022. WSDOT – Fish Passage Uncorrected Barriers Statewide. Distributed by Washington State Department of Transportation [cited 2023 Feb] from https://data.wsdot.wa.gov/arcgis/rest/services/Shared/FishPassageData/MapServer/8
Thank you to Misty MacDuffee and Darrel Zell for their files, contributions, and special knowledge.
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