SEATTLE — A conservation group plans to sue after net pens at a salmon farm in Washington state collapsed, spilling thousands of Atlantic salmon into Puget Sound.

The Wild Fish Conservancy says it gave Canada-based Cooke Aquaculture notice Friday that it will sue for violation of the federal Clean Water Act.

The company’s farm off Cypress Island held 305,000 Atlantic salmon, a non-native species. Cooke doesn’t yet know how many fish escaped.

The conservation group says the release poses a threat to struggling wild fish populations. It alleges the fish spill violates pollution laws because it sent farmed salmon, dead carcasses and other debris into the water.

Cooke spokesman Chuck Brown said in a statement that the company will review the group’s claim but is now focus on recovering the fish and preventing further releases.

State and tribal fisheries managers are urging anglers to catch as many as possible to protect native fish species.