Habitat loss threatens salmon

Law and Disorder: A Review of Habitat Legislation for BC’s Salmon Streams 2002
Werring, J. and D. Chapman. In Harvey, B. and M. MacDuffee (eds.) Ghost Runs: The Future of Wild Salmon on the North and Central Coasts of British Columbia. Raincoast Conservation Society. Victoria, BC. Pp. 149-163.

Salmon are faced with many threats to their survival (climate change, disease, animal predation).  One of the greatest threats to salmon is habitat loss. The following is only a sample of the many obstacles salmon face throughout their cycle:

  • Loss of access to historic habitat
  • Habitat destruction—loss of wetlands and side channels for spawning
  • Pesticide use
  • Aquaculture
  • Fishing harvest pressures
  • Dams and other impediments to fish passage
  • Flood control, dyking, and channelization
  • Gravel extraction from rivers
  • Illegal fishing
  • Industrial pollution, sewage, effluent flowing into rivers and streams
  • Urban development and encroachment onto riparian areas
  • Interference and harrassment from pets and people
  • Increasing water temperatures and pollution and garbage in streams

When adults return to spawn, they are threatened by lack of passage to natal or home streams. Returning adults are focused on reproduction. If their energy is depleted before they spawn, they die without producing the next generation of fish. Warming water temperatures and low water levels in streams also accelerate pre-spawn mortality.

Adapted from the City of Seattle’s Salmon in the City

Habitat Protection

Salmon are sensitive creatures (just as we are!). Following are some of the considerations we should keep in mind to keep salmon habitat as pristine as possible:

  • Keep gravel intact: Adult salmon females cover their eggs in gravel to protect them from light, gulls and ducks, and trout.
  • Preserve vegetation in the riparian zone: Eggs, young salmon, and tired spawners can be washed away by instant floods caused when plant and vegetation are removed from the riparian zone. Trees and shrubs around rivers and streams provide shade, and keep water temperatures from rising too high for the salmon. Among other problems, when water gets warmer, salmon need more food and may not be able to find it.
  • Allow water to flow: Waters unimpeded by dams or other obstacles are crucial for salmon as they migrate. They are attuned to moving water’s flow, and its push and pull rhythm helps them stay on course to their destination. (If waters go slack suddenly, salmon can abandon their migration entirely.)
  • Keep water levels constant: When water levels go up and down, the organisms salmon feed on are disturbed and salmon can starve.
  • Be responsible: Last but not least, salmon need responsible humans, in terms of their fishing practices and their overall behaviour!

Posted by Megan Moser in "Water & Habitat" on 9/15