Both king and fall chum salmon on the Yukon River show reluctance to form pulses
8-17-07
Tim Bodony

As the Yukon River king salmon run comes to an end, the fall chum season is getting underway. 

Many subsistence users along the river – in both Alaska and Canada - are planning to catch more fall chum than usual this year, to compensate for lower harvests of king salmon.   

But the fall chum run also seems to be later, and weaker, than expected this year. 

Timing of the runs has been late, numbers are down, and the fish have shown a reluctance to form into pulses when entering the river as they usually do. 

The Yukon king started with a strong pulse, but then fell off to a slow and steady trickle.  More recently, the fall chum started their run in a trickle without showing signs of life in the form of a pulse until a relatively late August 6^th.    

Before that, when trying to explain what was happening, Fish and Game’s reports straddled the fence, explaining that the fall chum could either be very late, or that this year’s run could be an unexpected failure.   

ADF&G Summer In-Season Manager Steve Hayes explains that different salmon species coming into the river bunch together as pulses in different ways, and that a variety of conditions might help, or discourage, the formation of pulses. 

Hayes:    For example, fall chum, they are very pulsey. They are very dependent on weather. Usually high winds, fall season type of weather it pushes them in in large pulses. Chinook typically tend to follow a pattern where we have the 3 to 4 pulses. What may end up keeping them from pulsing and coming in a more steady rate  could be later run timing, it could early on in the season the water is colder. There’s a lot of factors that could affect it. 

The first big pulse of fall chum salmon, estimated to be around 265 thousand fish in size, is heading up the Yukon River and a second pulse took shape this week as well.   

The fall chum intermingle with the far less desirable summer chum during late July and early August – but in possibly another unusual occurrence with Yukon River salmon this year, US Fish and Wildlife Service Yukon River Fisheries Manager Russ Holder suspects that the percentage of summer chum now moving upriver along with their fall season cousins is unusually high.   

Holder: The current projection that is being used in the ADF&G updates might be overly optimistic for the actual numbers of fall chum that are coming upriver. This first pulse that came through the lower Yukon is just getting analyzed by the genetics lab. We should know in 2 or 3 days what the genetics tell us about the proportion of summer chum versus fall chum.

Like the Yukon River king salmon that precede them, fall chum travel hundreds or thousands of miles upriver to spawn, with 25 to 30 percent of the run bound for Canada.  This means that a good number of fall chum are loaded with enough fat to make them a good eating fish, though a few notches below kings in quality.   

According to the 2002 Yukon River Salmon Agreement between the US and Canada, which was added to an earlier salmon treaty, Alaska managers are supposed to allow at least 80 thousand fall chum to enter Canada.   

Topping off the freezer with fall chum will be a top priority for fishermen on both sides of the border in the weeks ahead, as families try to supplement below-average king catches this summer.   

However, ADF&G estimates that the fall chum run will also be weaker than expected.   

The preseason projection was for a total run size of 900 thousand to 1 million fish; but after the run got off to late start, Fish and Game dropped that estimate to between 675 and 775 thousand, which according to its management plan, is still enough to open commercial fishing for fall chum throughout the Yukon River drainage.