Ecological Comment: The effect of dams on salmon

This is a nicely focussed perspective on the effects of dams on salmon written by second year Recreation, Fish and Wildlife students at Selkirk College in Castlegar, British Columbia – equally relevant to barriers in Scotland.

A hundred years ago, an estimated 16 million salmon migrated over 20,000 kilometres up the Columbia River basin. Today less than one million are only able to travel part way — 877 km to the Chief Joseph Dam in Washington.

With over 400 dams in the Columbia River basin, it is currently the most dammed river in the world. This has had an unfathomable effect on life all over the basin, but salmon in particular have suffered immensely. Dams have not only blocked the passage of these fish on the Columbia River, they’ve also caused other problems.

In the early years of dam construction, engineers ignored the value of aquatic life. Fish ladders and other passages were only introduced in 1927 but continued to be disregarded for many years. Twenty-eight years later, the Chief Joseph Dam was built, permanently blocking salmon migration to most of the Columbia River. Approximately 55 per cent of all spawning and rearing habitat in the Columbia River basin is now inaccessible due to dams.