Pacific Salmon population explosion

Pacific Salmon population explosion
While many Washington salmon species are listed as endangered, a new study found that the overall Pacific salmon population is the highest on record. However, that could be handicapping efforts to restore certain species. Photo: U.S. Geological Survey

As Washington stakeholders and policymakers explore ways to increase the state’s population of certain salmon protected as endangered species under federal law, the Pacific Ocean is contending with a different problem. According to a recent study, there are too many salmon, and that situation could very well be affecting recovery efforts for species that spawn and return to Washington rivers.

Although two endangered salmon species in Washington state have seen their numbers dwindle, there are more Pacific salmon now than at any time since record keeping started.  That was one of the conclusions of a new article by the American Fisheries Society (AFS). Yet the article also found that one type of salmon is overrepresented and could in fact be crowding out other salmon species, including those that return to the Columbia and Snake rivers.

Gregory Ruggerone, Ph.D. is a fisheries scientist for Natural Resources and coauthored the article with Dr. James Irvine, who lives in British Columbia. Ruggerone is also a member and former chair of the Independent Scientific Review Panel under the Northwest Power and Conservation Council.

He told Lens that “We’ve known salmon abundance has been high, but I guess it’s surprising it’s been so high in these recent years.”

In a press release, Irvine also said: “So we have to ask ourselves: Is it possible that there are too many salmon in the Pacific Ocean?”

The news may also come as a shock to Washingtonians fascinated by “The Blob,” a section of the Pacific Ocean where sea temperatures were higher than normal. Ruggerone says that the phenomenon was “a temporary event on people’s mind right now because it’s quite unique.”

At first glance, the record-level population may sound like good news, but that single statistic doesn’t tell the full story. Pink, chum and sockeye salmon are more abundant now than they have ever been since record-keeping first started in 1925, but other species such as chinook salmon in Alaska have seen their numbers decline.

One of the reasons for that could be overcrowding. More fish means less resources to go around, as the article cites a decrease in salmon survival. In fact, Ruggerone and Irvine argue the Pacific has reached the maximum salmon population it can sustain.

“If you look at the past 20 years, the total biomass of salmon in the ocean is flat, which is kind of intriguing,” Ruggerone said.

Another big takeaway from the article is that the salmon species aren’t represented equally; pink salmon alone compose 70 percent of the overall Pacific salmon biomass. The fish have relatively short lifespans of two years compared to chinook, which can live seven to nine years.

The large presence of pink salmon makes it difficult for struggling species to compete, Ruggerone said. The findings are similar to the conclusion of a 2016 study Ruggerone coauthored that found Bristol Bay sockeye salmon in the Bering Sea experienced fewer numbers and lower survival as the pink salmon population grew.

The salt in the wound for sports fisherman and others is that chinook “king” salmon is among the most desired. Not only are their numbers dwindling, but their overall size has decreased, something Ruggerone and Irvine also attribute to greater competition.

“If the North Pacific Ocean is at its carrying capacity with respect to Pacific salmon, the large numbers of Pink Salmon and Chum Salmon may be having detrimental effects on growth and survivals of other species,” Irvine said.

Also, there’s the relationship between the rise of pink salmon and hatchery-spawn salmon, which now make up 40 percent of both adult and immature salmon biomass in the Pacific. Most of them are pink salmon.

“Hatchery systems want more and more fish coming back to local areas, but the problem is…the hatchery fish migrate thousands of miles in the ocean and they compete for resources with other stocks,” Ruggerone said.

But that problem is originating outside Washington. The state Department of Fish and Wildlife (WDFW) operates 83 hatchery facilities primarily dedicated to producing salmon and/or steelhead. Another 51 hatcheries in Washington are managed by local tribes. There are also 12 federal hatcheries.

Yet only a handful produce pink salmon.  Instead, facilities such as the Issaquah Hatchery spawn chinook and coho, and occasionally the land-locked kokanee.

Issaquah Hatchery Executive Director Robin Kelley told Lens that each year WDFW tells them how many eggs to collect for each species, depending on their returning numbers. Most recently the hatchery collected three million chinook eggs and spawned 1,484 juveniles, an increase from the previous year.

“We heard chinook were down at other hatcheries, but they weren’t here,” she said. “It depends; each of the different areas have different impacts on them.”

One recommendation Ruggerone and Irvine make is for hatcheries to tag their salmon to get a more accurate estimate. It’s a practice WDFW already started in the 1990s but some Pacific-based countries have yet to follow this suggestion.

Regardless, Ruggerone says the overabundance of Pacific salmon is something to consider when discussing ways to improve endangered Washington salmon species. “It’s important for the Columbia River people to recognize that the ocean environment is dynamic and it certainly has an impact on the overall survival and abundance of the salmon returning,” he said. “But, they also have some important and critical habitat issues in the Columbia basin that they need to fix in order to enhance the survival.”

1 COMMENT

  1. The reporter here seems to misconstrue the scientific issues raised in the article. In addition, the headline is somewhat misleading. The authors of the study seem to be focused on the effects of hatchery production on available habitat and food in the Pacific. The increase in biomass, they observe, is largely hatchery-driven.
    In both legal and scientific examination, it has been determined that hatchery salmon and wild salmon are distinctly different species, and that hatchery fish are a detriment to the existence and recovery of wild fish.
    I had a lot of trouble parsing the meaning of this sentence: “Also, there’s the relationship between the rise of pink salmon and hatchery-spawn salmon, which now make up 40 percent of both adult and immature salmon biomass in the Pacific. Most of them are pink salmon.” I think this means there’s a lot more hatchery-raised pink salmon being released into rivers and oceans? Some clarification is needed. Regardless, the issue, it seems, is not so much a natural population “explosion” or “overabundance” but a detrimental overstocking of the ocean, due to overproduction at hatcheries around the Pacific.

LEAVE A REPLY

Please enter your comment!
Please enter your name here