Source: Wikipedia.

Source: Wikipedia.

A new study from researchers at Simon Fraser University argues that hundreds of small flood-control structures in the lower Fraser River are robbing salmon and other fish of valuable habitat while creating conditions for non-native species to flourish.

From The Vancouver Sun‘s profile of the research:

“The study looked at five sites with flood-control structures and five without in the Allouette, Pitt and Fraser systems, 44 to 57 kilometres from the ocean.

“Juvenile salmon were 2.5 times more abundant at the sites without floodgates and 11.7 times greater specifically for coho salmon, while prickly sculpin and native minnow were 37.2 and 11.7 times more abundant, respectively….

“The destructive power of larger dams to fish habitat is well known, but the influence of smaller-scale flood-control structures is much less documented. Floodgates typically are designed to close during high tides and the spring freshet to prevent upstream flooding into farm fields and urban areas.

“The problem is that the floodgates can also block the passage of fish and create low-oxygen zones in which certain non-native species can survive. Pump houses often associated with the floodgates can also be lethal to migrating fish. In late summer and fall there may also not be enough downstream flow to open the floodgates, a problem that could be resolved by forcing the gates open.”

Read more from the article here.