Anadromous Fish Stressors
Man-made barriers to fish passage include road/stream crossings, irrigation diversions and dams. Passage impediments and delays in migration affect both adult and juvenile fish. Given the magnitude and severity of the problem, reconnecting isolated stream habitat has become an important priority in restoring anadromous fish populations. Common factors that adversely impact fish populations in California’s anadromous waters include:
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changes in runoff patterns and water storage
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land-use and natural resource extraction activities
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spatial and temporal changes in connectivity
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non-native species introductions
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increased predator populations
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commercial and recreational fishing
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hatchery operations
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natural environmental variations
Anadromous Fish Species Affected by Passage Barriers in California
California streams and rivers have historically been home to several native anadromous fish species. These include Chinook salmon, Coho salmon, Steelhead/rainbow trout, Coastal Cutthroat trout, Green sturgeon and White sturgeon, Pacific lamprey, Eulachon, and Threespine stickleback. Historically, anadromous fish passage efforts in California have focused on Chinook salmon, Coho salmon, and Steelhead. Pink salmon have only occurred rarely in California since the latter half of the 20th century. Chum salmon are slightly more common than pink salmon, but are still highly limited in California.
Why Address Connectivity? Removing Barriers to Connectivity Improves…