Scientists are certain of one thing certain about the decline of Yukon River king and chum salmon There’s more than one person to blame.
“It’s extremely difficult and possibly impossible to make a point about something and claim this is what’s happening,” said Jayde Ferguson who is a fish pathologist at the Alaska Department of Fish and Game.
Researchers have identified a myriad of risks faced by Yukon salmon, including chum and king and these threats appear at every phase of the salmon’s life cycle. This includes when the fish hatch in freshwater streams, and as they swim through the Yukon towards the ocean in which they spend the bulk of their lives. They also face danger during their long trip back upriver to spawn, and then die.
Researchers believe that many of these risks are related with climate changes. Ferguson is studying one the parasite ichthyophonus in the Alaska Department of Fish and Game laboratory in Anchorage.
Under microscope, the salmon tissue that is infected by ichthyophonus looks smudged with white dots that are large, each a parasite that grows and drain the resources of the fish and the cells will die.
The parasite doesn’t cause harm to people, yet it can cause death to fish. When salmon make their way to the river and downstream, they’re particularly susceptible.
“Their immune system isn’t as effective Their bodies are being destroyed,” Ferguson said. “And this is why the parasite begins reproducing in the body of fish.”
Infected fish are often not able to remain for long enough to lay eggs.
“It’s something like the arms race” He said. “Can they make it to the ground of spawning before they’re dead?”
In most cases, the fish that are infected appear identical from the outside, however their flesh is likely to have an spotted or patchy white pattern that indicates the parasite is growing within. It is important to note that infected fish are not suitable for eating.
Researchers noticed a huge spike in king ichthyophonus levels at the beginning of 2000, when about 30% of the monarchs had detectable levels. The levels dropped for over 10 years. Then, in the year 2020 the parasite returned. Recently, over 40 percent of the Yukon King Run has been found to have an ichthyophonus presence that is detectable.
It’s not clear what’s causing the rise. Other studies have revealed that Yukon King Salmon eggs lack the vitamin thiamine which could lead to weakened immune systems. Ferguson suggested that warming water in the river could also be a factor.
In fact, the Yukon is warming twice as fast as rivers further south as a result of climate change.
“It’s insane to be in the northern range of salmon and talk about the heat being too hot,” said Vanessa von Biela who is an U.S. Geological Survey ecologist.
They are cold-blooded which means they don’t have the ability to manage their body temperature. If the temperature of the water rises higher than 65 degrees Fahrenheit this is an issue.
When temperatures are too hot, Von Biela said, the proteins that help keep the salmon cells operating normally begin to shrink in size. The warm water makes it difficult for their heart to supply oxygen to their bodies.
“Their entire anatomy, their whole body, is designed to function at a cold temperature,” the doctor said. “So when that water gets warm, they really exceed these limits.”
In an study for 2020, von Biela found that, in an average year, the majority of Yukon Kings who swim upriver experience heat stress.
It’s not only the river that’s warming. The ocean is warming up as well. Changes in climate are causing more heat waves in the ocean or extreme ocean warming.
Jim Murphy is a NOAA fisheries biologist who has been studying the sea salmon for over twenty years. He believes that the heat waves in the ocean are affecting the availability of salmon’s prey species. It’s unclear what’s happening in the ocean, Murphy said, but when he studies the fish, there is one thing that is evident that all salmon and especially chum aren’t getting enough to consume.
“Their stomach contents and the amount of food that’s in their stomachs is declining as they warm temperatures” Murphy said. “They’re likely to be eating less during the warmer months than they do in the cooler months.”
Researchers say that each of these three elements such as heat waves, and a deficiency in food can exacerbate each the other. Fish that don’t eat enough is already weaker before it begins its journey through the Yukon. Add in a parasite or the stress of heat that makes the fish much less likely to reach the spawning ground to reproduce, which will mean fewer fish in the coming year.
Yukon River fish also have one of the longest migration routes for salmon on Earth and can travel as long as 2,000 miles to their eggs’ spawning areas.
In addition to this those living who live along the river face another issue: commercial fishing. A lot of residents refer at Bering Sea pollock trawlers and commercial salmon fisheries in the Aleutians referred to by the name of “Area M” they believe are taking salmon from the sea which would otherwise be headed to the Yukon.
“It sort of piss me off when I think about it. Because it’s a double standard,” said Basil Larson who is a subsistence fisherman who lives in Russian Mission, on the lower Yukon. He was a guest speaker on an annual Yukon River Drainage Fisheries Association webcast to update the river this summer.
Larson stated that it is awry to watch commercial fishermen pull in a swath of chum. the chum every season, whereas Alaska Native communities like Russian Mission have endured four summers just barely able to catch fish.
“We’ve been getting restricted, restrained and it’s not amusing anymore” the man said.
In recent times, Western Alaska fisheries groups and people living in those living in the Yukon as well as the Kuskokwim Rivers have demanded stricter sea regulations such as the introduction of a limitation on fishing chum in the area M, and more strict Chum limit on bycatch for the Bering Sea. But the regulators have not taken any action.
Commercial fishermen draw attention to the fact that only a tiny portion of Bering Sea bycatch salmon and Area M salmon are heading to Western Alaska rivers.
However, Murphy is with NOAA stated that, while environmental influences triggered by climate change may be the primary cause of that Yukon collapse, at present commercial fisheries is sole factor we can control.
“Most people realize that [commercial fishing] isn’t what is responsible for the collapse of these fisheries, but it is. However, it’s something that can be controlled to reduce the impact of a decline in output,” Murphy said.
At present, Yukon River residents are in limbo and waiting to find out if the fish will return. Murphy stated that it doesn’t seem like kings will be returning any time in the near future. But he did say there’s a chance for the chum.
The 2016-2019 Bering Sea heat wave hit Chum salmon particularly hard however, since then, the ocean temperatures have slowed down and Murphy stated that juvenile chum appear to be getting healthier.
He also said there are signs for a better chum to run 2024.
