PORTLAND — A coalition of environmental and fishing groups filed a federal lawsuit Wednesday against Oregon, alleging logging in the state’s two largest forests is threatening the survival of coho salmon that breed in streams flowing through the coastal region.

The lawsuit filed in U.S. District Court in Eugene challenges the state’s logging policies in the Clatsop State Forest and the Tillamook State Forest.

It alleges the Oregon Department of Forestry is in violation of the U.S. Endangered Species Act because of the logging, and is illegally engaging in activities that result in the death of a threatened species.

The agency has not followed through on implementing a species management plan required under federal law that would help preserve salmon habitats despite logging and mitigate damage, court papers allege.

Ken Armstong, a spokesman for the Oregon Department of Forestry, said his department could not comment on pending litigation.

“Poor logging practices by the Oregon Department of Forestry is causing real harm to the Oregon Coast coho and commercial fishing families who depend on these magnificent fish for their livelihoods,” said Glen Spain, the northwest regional director for the Pacific Coast Federation of Fishermen’s Associations and the Institute of Fisheries Resources, both plaintiffs in the case.

“Stronger protections for streams to protect the coho … is decades overdue.”

Together, the forests cover a half-million acres stretching from the Washington state border to the central Oregon coast.

About 2,500 miles of roads have been built in them to accommodate logging, according to court papers.

Logging activity increases the risk of landslides and of sediment falling into the streams where the salmon breed and grow to maturity before venturing to the Pacific Ocean.

Seven streams critical to salmon habitat flow through the Tillamook State Forest and several others run through the Clatsop State Forest, according to the lawsuit.

Between 1 and 2 million salmon returned to their natal streams in this region — an area stretching from Seaside to Port Orford — in 1900.

The number of returning coho salmon has now dropped below 76,000, court papers say.

Other plaintiffs are the Center for Biological Diversity, the Native Fish Society and Cascadia Wildlands.

Mark Morgans, area manager of the Lewis & Clark Timberlands for Greenwood Resources, is not convinced the lawsuit’s claims are justified by scientific research. But even a lawsuit that focuses on the state has the potential to impact private timber enterprises, he said.

“If a political — not biologically justified — decision is made to change forestry regulations on public land, then proponents typically assert those changes should occur on private land, too,” he said.

“Society may choose to change how their lands held in public trust are managed for some perceived value and then we all pay those costs.”

Morgans manages private timberland but said companies like Hampton Lumber, with a mill in Warrenton, rely on several sources for raw material, including state timber sales, private timber sales and outside purchases. Increased regulations could negatively impact that business as well as the vendors they supply.

Katie Frankowicz of The Daily Astorian contributed to this report.