The number of Yukon River chinook crossing into the Yukon has punched above 42,500, or the minimum target for meeting spawning objectives.

It represents the fourth summer in the last eight seasons that the target number has been reached.

The benchmark was hit Tuesday at the Eagle, Alaska sonar just below the Yukon-Alaska border.

The sonar estimates 3,275 chinook passed by yesterday up to midnight, representing the largest single-day count since the first fish was recorded at Eagle on June 27.

With mounting concern about the future of the Yukon River chinook stocks, authorities on both sides of the border implemented a zero-catch management plan for this season.

While there’s been no commercial and sport fishing allowed for a number of years now, it’s the first time for a full closure of the Yukon’s aboriginal food fishery and Alaska’s subsistence fishery.

The Yukon Salmon Sub-Committee, backed by the support of First Nations, called upon the Department of Fisheries and Oceans (DFO) to impose the closure.

First Nations have expressed dire concern about the dwindling chinook stocks, not only because of the shrinking availability of traditional food, but also because of how closely the salmon are tied to their cultures.

At least one First Nation has suggested a full closure of at least one entire life cycle – seven or eight years.

Scientists agree the chinook returns are weakening, and they acknowledge they do not know why.

Last year, an estimated 30,573 crossed into the Yukon, compared to 34,656 the year before and 50,901 in 2011.

The most recent big year, according to official records, was in 2003, when an estimated 90,037 chinook crossed the border.

This year’s closure of the aboriginal food fishery was contingent upon reaching the 42,500 mark.

Once the minimum escapement goal was reached, the federal department was to talk with the First Nations and the salmon sub-committee about the possible harvest of some chinook.

The DFO’s area director was in meetings this morning and unavailable for comment.

Alaska salmon scientist Dr. Stephanie Schmidt has been tracking the strength and composition of this year’s run. She’s estimating a total of 52,000 chinook will cross the border.

Back in the days of seemingly plenty – not 20 years ago – the total annual harvest on both sides of the border could easily exceed 150,000.