Lead researcher Benoit Lalonde said they looked at the health of benthic invertebrates, "the building blocks of what lives in the river or the stream" in areas where water that passed over hatcheries flowed.

Benthic invertebrates are small creatures that live in or on the bottom sediments of rivers, streams and lakes and include immature mayflies and caddisflies.

Researchers found significant changes in biodiversity at two of the sites and some differences at a third.