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FACTORS RESPONSIBLE FOR THE DECLINE IN SALMON ABUNDANCE AND DISTRIBUTION IN THE PACIFIC NORTHWEST
MAJOR FACTORS Agriculture: 1, 2, 4, 5, 6, 8, 9, 10, 18, 21, 22 Fishing: 16, 19 Dams: 9, 11, 18 Forestry: 1, 2, 4, 6, 7, 10, 21, 22 Drought: 9, 10 Urbanization: 1, 3, 5, 6, 7, 8, 9, 10, 11, 21, 22
POTENTIALLY IMPORTANT FACTORS * Gravel Harvest: 6 Hatchery Fish Interference: 19, 20 Irrigation: 9, 12 Poor Ocean Conditions: 13, 14, 15, 16 Bycatch Mortality: 16, 19 Illegal Fishing: 16, 19 (salmon killed during fishing for other species)
MINOR FACTORS Bird Predation: 17 Marine Mammal Predation: 16, 17
Components Of The Factors Causing Salmon Decline 1. Loss of Streamside Vegetation and Functions 2. Pesticide Exposure 3. Industrial Pollutants Exposure 4. Increased Amount Of Sediment Entering Streams 5. Stream Straightening and Channelizing 6. Habitat Destruction 7. Decreased Amount Of Large Logs In Streams And Loss of Deep Pools and Channel Form 8. Filling of The Side Channels of Streams 9. Reduced Fresh Water Flow In Rivers and Streams 10. Exposure to Abnormal Temperatures 11. Habitat Area Loss 12. Lack of Screening of Water Diversion Canals to Keep Fish Out 13. Reduced Upwelling 14. Altered Ocean Currents and Flow 15. Decreased Food Abundance 16. Reduced Numbers of Adults Reaching Their Spawning Grounds 17. Reduced Numbers of Young Fish Making It To The Sea 18. Barriers Preventing Salmon From Migrating Upstream or Downstream 19. Loss of Genetic Integrity and Diversity 20. Competition Between Hatchery and Wild Fish 21. Forest Fragmentation 22. Estuary Degradation * Insufficient data exists for an appropriate assessment of magnitude. Table based on studies of rivers in Western Oregon and Northern California. Adapted with permission by Pacific States Marine Fisheries Commission from Status and Future of Salmon of Western Oregon and Northern California: Overview of Findings and Options by Botkin, Cummins, Dunne, Regier, Simpson, Sobel, and Talbot. For a copy send $17 to The Center for the Study of the Environment, P.O. Box 6945, Santa Barbara, CA 93160.