TULALIP — After several years of negotiations, the Tulalip Tribes and the state have reached an agreement for joint management of hatchery Chinook salmon aimed at rebuilding stocks of the threatened species.

The agreement, the first of its kind in the Puget Sound region, sets joint goals for the number of juvenile fish to be released and for adults that return to rivers.

For years, staff at the Tulalips’ Bernie “Kai-Kai” Gobin Hatchery and the state’s Wallace River Hatchery near Sultan have worked together in recent years and this agreement will increase the level of cooperation that much more, officials said.

As part of the agreement, the Wallace River Hatchery will release twice as many yearling Chinook salmon as it does currently — increasing the total from 250,000 to 500,000, said Heather Bartlett, a hatcheries division manager for the state Department of Fish and Wildlife.

This will generate more hatchery fish to be caught, reducing the chance that spawning wild fish will wind up on the end of a hook or in a net.

On the Tulalips’ end, the tribes will continue their program of tagging and marking their own hatchery fish to help keep them from mingling with wild stocks. The tribes also will supply manpower to the state to help monitor fish that return to the Wallace River via the Snohomish and Skykomish rivers, said Mike Crewson, fisheries enhancement biologist for the tribes.

Hatchery fish are produced mostly for harvest to lessen the impact on Puget Sound wild Chinook, which have been listed since 1999 as threatened under the federal Endangered Species Act. Most hatchery fish return to the area in which they are released but do not go upstream to spawn, but there are exceptions. While spawning hatchery fish can be helpful in long-term fish recovery, mixing hatchery and wild stocks also can cause genetic mutations that weaken the wild fish, so it all has to be closely monitored, Crewson said.

“Tagging and marking ensures that reliable monitoring will occur that will show the Tulalip and Wallace programs are not adversely impacting the wild fish,” he said.

The agreement, Crewson said, “cements in place the marking and tagging at both facilities.”

Using eggs from fish raised at both their own hatchery and at Wallace River, the Tulalips raise and release Chinook, coho and chum salmon into Tulalip Bay. This provides a fishery for the tribes and is open to non-tribal anglers as well, without affecting wild stocks.

The fingerlings, like their wild counterparts, grow and go to sea. If they survive, they return to Possession Sound and the bay, where they may be caught.

The state aims to strike similar agreements in other parts of the state.

The agreement, Crewson said, strengthens the co-management of fisheries by the state and the tribes.

“All this is done by both of us,” he said. “It’s a really positive thing.”

Bill Sheets: 425-339-3439; sheets@heraldnet.com.