By Gale K. Vick, Fairbanks Fish & Game Advisory Committee Member
We know that getting more fish to the spawning grounds is a goal for rebuilding Chinook and chum stocks in the Yukon River Drainage, but we may not have considered the more nuanced concern over age, sex and length and what that means to the productivity of salmon beyond just counting fish.
With the extreme decline of Chinook and chum stocks, demographics and productivity often get overlooked in our discussions. However, these factors become more critical as we think about regrowing the stocks of salmon in our rivers. The Yukon has not met escapement goals in most of the Alaska-side tributaries for years. Chinook are getting smaller and thinner and the dominant year classes are getting lower, meaning the fish are spending less time maturing in the ocean before they come back to spawn. The situation is so bad for Canadian-bound Chinook that a new agreement with Canada requires a seven-year moratorium on catching Chinook for any purpose beyond limited harvests for ceremonial purposes.
While Pilot Station numbers are only estimates of passage and not escapement, it is the entry into the river measurement by which the Alaska Department of Fish and Game (ADF&G) determines fishing opportunity. There is a 90% confidence level attached to the passage estimates.(1) This chart from 2016-2023 tells us part of the story of a long-term decline for Chinook and fall chum especially.
But our reliance on just numbers may have been insufficient for decades in assessing Canadian and Alaska-bound Chinook and fall chum abundance. For instance, without truly assessing productivity on the spawning grounds and by utilizing gear types that target bigger fish, we may have inadvertently hastened the demise of big Chinook genetics.
Size reduction equals less ability to produce an abundance of offspring, or fecundity, in females, leading to fewer eggs on the ground. Productivity of salmon spawners is linked directly to the fertility of female fish. Along with egg size, egg number is closely related to the reproductive potential of a spawning population. Getting BOFFFFs (big, old, fat, fertile, female fish) is the primary goal for increasing the chances of salmon to survive.
As a female Chum salmon grows larger so too does the number of eggs she will be able to produce when spawning. These eggs will also be larger because she is able to devote more energy to developing them. Over time, scientists have found that the size of the Chum salmon on the Yukon is shrinking due to factors related to biological and environmental variables, which means that the Chum that are running now will produce fewer and smaller eggs than those that ran in previous generations.
Measuring fertility is one of the most difficult tasks in assessing salmon health. Monitoring hundreds of salmon streams within the Yukon River drainage is an almost impossible task. It’s a discussion we should be having relative to planning, educational materials and community based monitoring options.
Between Pilot Station and Eagle Station border crossing, there are almost 1,200 river miles, with another 800 in Canada. That’s a long way to travel after coming in from the ocean, and it can often take weeks for salmon to reach spawning grounds. Since migrating salmon are no longer feeding, they use up body energy stored in fat reserves with each mile upstream. This is all the more reason to protect the bigger fish. There is a single certainty; once a pre-spawning female salmon is taken out of the water for any reason, its contribution to productivity is lost.
This goes to the heart of handling practices en route. Gear type becomes extremely important in the effort to protect pre-spawning females. This is why there is so much emphasis on reduced net mesh and utilizing dip nets as conservation gear.
Aside from in-river conservation measures to protect the age, sex, and size of salmon, we are all keenly aware there are still major impacts of ocean conditions, prey, competition for food, bycatch and intercept that we must continually monitor and factor into our conservation plans. There are many ways we can help salmon stocks rebuild. Monitoring safe passage and productivity on the spawning grounds is at the top of the list.
1 – JTC/ Joint Techinical Committee 2023 season review / Yukon River Panel