What Makes migration Tough for Fish? Identify the obstacles and check your answers on the right! Predators intercept migrating fish in coastal waters. water discharge may degrade quality. Waste See 5. Fish trapped below culverts can be easy prey for birds. See 5. See 4. Abandoned dams are also unsafe. ago, rivers were straightened so logs could get to mills. This degraded fish habitat. Years Warming of rivers and oceans can impact fish survival. Warming A west coast elephant seal may prey on migratory fish. An east coast harbor seal may prey on migratory fish. The brown pelican is a natural predator of migratory fish. cooling process. Intake pipes can suck juvenile fish into the industrial plant’s Abandoned dams used during the log drive days continue to block fish migration. See 5. Undersized culverts also disrupt natural flow and sediment transfer. A changing climate can alter oceanic currents vital to migratory fish. 8. 9. 10. 11. 12. 13. 14. 22. 23. 24. 25. 26. 27. 28. 29. Grazing cattle can damage river banks and degrade water quality. Runoff from fertilizers can degrade water quality. Irrigation can reduce water levels; remaining then become too warm for native fishes. Historic mill dams can affect the natural flow of rivers and prevent fish from migrating. round culverts tend to hinder or totally block fish movement. Traditional Non-native fish prey on juvenile migratory and disrupt the food chain. fish. Dams may delay or totally prevent migration and altered flow favor non-migratory and/or non-native Migratory fish may be legally harvested in other countries; here they are sold a market. Many species of birds eat migratory fish. Some migratory fish are intercepted at sea en route to and from spawning habitat. Migratory fish are an important food source for birds like bald eagles. Air pollution from factories and sewage treatment plants can degrade water quality. Migratory fish may be an unintended bycatch in fisheries targeting other species. Migratory fish are an important natural food source for birds like ospreys. 1. 2. 3. 4. 5. 6. 7. 15. 16. 17. 18. 19. 20. 21.