Study shows trout thrive after Oregon coastal logging

Ashley BachBLOG

A new study shows that modern logging in the Oregon Coast Range, under the auspices of the Oregon Forest Practices Act, had no negative impact on cutthroat trout and coho salmon.

In fact, the study showed that the number of cutthroat trout actually went up in the harvested area, compared to an area that wasn’t harvested.

Starting in 2006, a team of researchers from Oregon State University, the U.S. Geological Survey, Colorado State University and the forest products industry returned to the Alsea basin to study the impacts of modern logging practices conducted in compliance with the act. They assessed the numbers of cutthroat trout, aged one year old and older, annually through 2014 in the watersheds of Needle Branch and Flynn creeks. The researchers also documented forest cover, stream habitat conditions and stream temperature and discharge.

Logging occurred in Needle Branch in 2009, but Flynn Creek was left unharvested, just as it had been in the 1960s. The results were published March 1 in a professional journal, Forest Ecology and Management.

…(In the study,) the biomass of cutthroat trout in Needle Branch increased after the tree harvest relative to the trout in Flynn. In the headwaters area of Needle Branch, nearly all of the trees were cut with the exception of the required buffer strip along the fish-bearing portion of the stream. By monitoring the movements of fish up and downstream, the researchers were able to determine that increases in Needle Branch were related to local changes rather than to influxes of fish from other areas.

Researchers said they do not know why the trout numbers improved in the harvested area compared to the unharvested area, but the findings are encouraging.

“We can confidently say that, in this watershed, cutthroat trout were not negatively affected by logging activities over the course of the study,” said (Doug Bateman, the lead author of the paper, now a retired Oregon State University researcher). “We’re cautious about generalizing these results to other watersheds since conditions can vary so much. Still, these fish are probably well adapted to changes in the streams, and forests provide some of the best remaining habitat for them. When you move downstream into areas adjacent to farm fields and urban areas, the changes to rivers and streams can pose significant challenges. It’s important to look at the watershed as a whole.”