OPINION: Red herrings won’t help us save chinook salmon

While I’m an Alaska whale biologist, I’m as concerned about declining chinook salmon numbers as I am any marine mammal. Chinook, or king salmon, are essential to a healthy Alaska, for people and wildlife. To protect and recover chinook salmon, and the entire Alaska marine ecosystem, we must focus on the real root causes of their decline and avoid scientifically groundless distraction and unnecessary division. Blaming killer whale predation is not the answer.

New studies by the Alaska Department of Fish and Game conclude the problem with Alaska’s chinook salmon populations can be linked to their declining survival while in the ocean. A recent opinion by Andy Wink claimed that killer whale predation was likely a driving factor. Blaming predators for declines in prey populations has always been a popular notion in the minds of us humans, and predators can certainly have a serious impact on prey populations in some situations. But is there good evidence killer whales are driving chinook salmon declines in Alaska? The science doesn’t support it.

Wink’s opinion threw around a lot of impressive predation numbers. But these numbers appear to come from a 2017 Oregon State University research paper, which assumed high levels of chinook consumption by killer whales throughout the North Pacific based on early diet studies in the Pacific Northwest. This study is not representative of killer whales in Alaska, nor Russia or Japan. Moreover, recent work by a NOAA Fisheries science team describes a more diverse year-round diet for that Pacific Northwest killer whale population, known as Southern Resident killer whales, even though chinook salmon remain important in their diet, particularly in the summer.

A long-term diet study of killer whales in the northern Gulf of Alaska by my organization, the North Gulf Oceanic Society, showed that chinook salmon are dominant in orcas’ diet only in a specific location, Resurrection Bay near Seward, and only for a one-month period in the spring around the Aleutian Islands, where fish-eating killer whales are particularly abundant. Our research and that of NOAA Fisheries has found scant evidence of extensive killer whale predation on Alaska chinook, possibly as low as 25%-40%. In other words, the actual predation by killer whales on chinook salmon in Alaska is likely far lower than the numbers implied in Wink’s opinion.

Wink also highlights the declining size and abundance of chinook but does not mention that the size of killer whales is also declining. Research by members of our team has shown that the body size of both Southern and Northern Resident killer whales in Washington and British Columbia, respectively, declined for whales that were maturing during periods of reduced chinook abundance in the 1990s. This suggests that the whales are responding to the declines in chinook salmon, rather than driving it.

Absent from Wink’s opinion was any mention of the role of competition facing chinook salmon in the ocean. Recently, a study by scientists at the University of Alaska provided strong evidence that huge hatchery production of pink salmon, which now comprise around 40% of the biomass of salmon in the North Pacific, may have unintended consequences for wild salmon, including chinook salmon. It appears these hatchery pinks directly compete with wild fish and are causing fundamental changes to the North Pacific ecosystem. I was a commercial salmon fisherman for 20 years and directly benefited from the hatchery production in Prince William Sound. However, massive returns of hatchery pink and chum salmon have ecosystem repercussions. The marine ecosystem provides no free lunches.

Climate change isn’t helping, either. The 2014-16 marine heat wave in the Gulf of Alaska severely harmed chinook salmon, and a large collaborative research paper led by NOAA Fisheries researchers reported an associated decrease in the harvest numbers for chinook salmon, and widespread ecosystem disruption in general. To think that climate change is going to be a boon to fishes in our northern waters is naïve at best. The most recent example is the collapse of the snow crab fishery due to the most recent marine heat wave. This well-documented marine heat wave was the first major climate-change driven assault on the Alaska marine environment. It certainly won’t be the last nor the worst.

To protect and recover chinook salmon, it is important we keep our attention focused on the root causes and work together to address them, rather than blame secondary effects like marine mammal predation. These scientifically unfounded distractions slow salmon recovery and divide our community. They also ignore the many positive benefits marine mammals provide ocean ecosystems, like cycling nutrients and strengthening the marine food web, benefiting all species, including salmon. It’s time to bring a clear focus to ecosystem changes and address the main likely drivers of the chinook salmon’s woes in Alaska — hatchery salmon and the changing climate.

Craig Matkin is the executive director of the North Gulf Oceanic Society based in Homer. He is a whale biologist with more than 40 years of Alaska experience.

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