Copper - one more reason Pebble Mine threatens Bristol Bay's salmon

There are many reasons that Pebble Mine, the proposed copper and gold mine in southwest Alaska’s Bristol Bay area, would threaten one of the most productive salmon fisheries in the world.  As we have been highlighting here, operation of the mine could cause the partial or complete dewatering of miles of freshwater streams; construction would include the development of roads that could cross numerous known salmon streams; waste products would be stored in large tailing ponds that could leak toxic elements into the surface and groundwater.  These types of impacts on the salmon fisheries are perhaps the most obvious.

One of the greatest threats to the fish, however, might not be the byproducts of the mine and its construction, but the target of the mining operation itself: copper.

Copper is naturally occurring in the environment, but if copper levels increase even slightly above naturally occurring levels, it can be toxic to fish and other aquatic life.  Certain activities such as hard rock mining can lead to elevated levels of copper in surrounding waterways which is why there are established water quality thresholds for copper (and other metals).  Research shows, however, that copper can affect salmon and their food chain even at levels below these established thresholds. 

For example, increases in copper – even small increases that comply with federal regulations -- can interfere with salmon’s ability to smell and sense vibrations which has been shown to put salmon at a greater risk of predation.  A lack of smell or changes in the water chemistry of an area also can inhibit salmon’s ability to migrate and accurately find their natal habitat.  In addition, increases in copper can kill algae, zooplankton and aquatic insects all of which provide a major food source for salmon.  Finally, increases in copper can kill freshwater mussels which are a food source for humpback whitefish – a subsistence fish in the Kvichak watershed.  Humpback whitefish, in turn, are a food source for salmon.

The effect that copper will have in any given waterway is influenced by a number of variables and is therefore hard to predict.  However, this research indicates that even if Pebble mine were able to strictly comply with the established water quality standards, salmon in the area could still suffer detrimental effects.  While additional research will help us better understand site specific consequences of increased copper under different water conditions, the available data already clearly indicate that building a massive copper mine in the heart of one of the most productive salmon fisheries in the world is simply not worth the risk.

Please take a minute to sign our petition opposing Pebble Mine.  We will deliver the petition to the British mining giant Anglo-American, at its annual shareholder meeting on Earth Day.

Bristol Bay Sockeye Salmon

Image: Bristol Bay Sockeye Salmon shared by toddraden via Flickr.

About the Authors

Sylvia Fallon

Director, Wildlife Conservation project

Join Us