Pacific salmon ‘more abundant than ever’, new study claims

Business In Vancouver

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Pacific sockeye are one of three salmon populations that are doing well, according to a new study?|?Iryna Harry/shutterstock

Pacific salmon are generally “more abundant than ever.”

That is the provocative conclusion of a new paper published in Marine and Coastal Fisheries by Greg Ruggerone of Seattle’s Natural Resources Consultants and James Irvine of the Department of Fisheries and Oceans.

The study used historical commercial catch and escapement data for the entire Pacific region for both wild and commercial hatchery salmon over a 90-year period, up to 2015.

There is one caveat, however: Ruggerone and Irvine analyzed only data for pink, chum and sockeye salmon.

Had they included other species, like chinook, coho and steelhead, the picture might look different, because those species have declined in some regions, especially the more southern ranges, like B.C.

Ruggerone and Irvine focused exclusively on pink, chum and sockeye because they are historically the most abundant species, and there is more historical catch and escapement data available. Historical data for other salmon species is spotty at best.

They point to a massive injection of hatchery salmon – mainly pink and chum – from Alaska, Japan and Russia augmenting their abundance.

The study shows wild salmon abundance peaking between 1934 and 1943, then declining until about 1977, when an ocean regime shift began boosting their numbers again.

From 1990 to 2015, pink salmon accounted for 67% of the total abundance, followed by chum at 20% and sockeye at 13%.

Chinook, coho and steelhead represent only 4% of the total salmon catch.

Pink salmon have historically been the most abundant species in the Pacific. Of all salmon species, they appear to be the least in need of help from hatcheries.

But they are favoured by the commercial fishing sector over other species because pink and chum migrate to sea soon after hatching, so there is no need to rear them for a year or two, as is the case with other species. In other words, it’s cheaper to pump out pink and chum salmon from hatcheries than other species.

About five billion hatchery fish – mostly pink and chum – are released annually into the Pacific Ocean from hatcheries in Japan, Alaska and Russia. Alaska is the biggest producer of hatchery pink salmon.

Irvine and Ruggerone estimate hatchery fish accounted for 40% of total biomass of the three species examined between 1990 and 2015 – the period when commercial hatcheries were increasing production.

They estimate that 48% of the commercial salmon catch in Alaska is hatchery fish.

“In this part of the world, its kind of all doom and gloom,” Irvine told Business in Vancouver. “Salmon stocks, there’s lots of concerns about populations being extirpated. From a really big-picture perspective, salmon, as a whole, are really doing well.”

But are they doing really well at the expense of other species, like chinook? And if so, are they getting too much help from hatcheries? Or are they simply winning Darwin’s race by adapting to changing conditions better than other species?

Ruggerone believes hatcheries are giving pink salmon a competitive edge, at the expense of other species.

“While it is good that abundance of sockeye, chum and pink salmon is high, there’s growing evidence that this high abundance, especially pink salmon, is impacting the offshore ecosystem of the North Pacific and Bering Sea,” Ruggerone said.

“This impact may be contributing to the decline of higher trophic species of salmon, such as chinook salmon, in Alaska. Hatchery salmon are exceptionally abundant now, and contribute to this impact.”

Brian Riddell, president of the Pacific Salmon Foundation, agrees that hatcheries for chum and pink are contributing to the abundance of juvenile salmon in the North Pacific. But he points out that hatcheries have also been used to try to bolster chinook, coho and steelhead “with very mixed results.”

And as the Irvine-Ruggerone study data points out, sockeye have been relatively abundant in recent years – especially in Alaska – despite the fact that hatchery production of sockeye has been comparatively low.

“Recent high marine abundances of both natural- and hatchery-origin salmon could be interpreted to indicate little or no adverse interaction between these groups,” the study acknowledges. “However, considerable evidence exists that salmon compete for food at sea, which can lead to reduced growth, delayed age at maturation and reduced survival.”

If an abundance of pink salmon, augmented by hatcheries, is having an impact on species like chinook, that should raise red flags for scientists concerned about a decline in the southern resident killer whale population, because chinook salmon make up 90% of their diet.

A decline in chinook has been particularly pronounced in the Fraser River populations in recent years. Escapement data shows their numbers ranging from 137,000 to as high as 256,000 between 2005 and 2011, and then dramatically falling to 37,000 and 35,000 in 2012 and 2013, respectively.

Chinook numbers in Alaska have also been so low in recent years that sport and commercial fisheries in the state are being dramatically curtailed this year.

Chinook are not just shrinking in number – they are literally shrinking in size. A recent study led by Jan Ohlberger from the University of Washington’s School of Aquatic and Fishery Sciences notes that chinook throughout most of the Pacific Ocean have been declining in size and maturation over the past four decades.

Part of the reason might be that fishermen target the larger fish. But so do northern and southern resident killer whales.

“While it remains to be explored whether these trends are caused by changes in climate, fishing practices or species interactions such as predation, our qualitative review of the potential causes of demographic change suggests that selective removal of large fish has likely contributed to the apparent widespread declines in average body sizes,” the study concluded.

Charles Swanton, deputy commissioner of the Alaska Department of Fish and Game, isn’t convinced that hatchery fish are competing with chinook, because they tend to have different diets.

“They have pretty defined forage preferences,” he said. “There may be some overlap, but it’s not direct in terms of something that you could pin down as being directly competitive.”

While it’s true pink salmon don’t eat the same food as other species in their early stages, as they mature there is some crossover, Ruggerone said.

Pink salmon are especially abundant in odd years, and as a consequence, he said, the diet of chinook salmon changes in those odd years.

“You see a change in the diet of chinook salmon. In those odd-number years, the consumption of food is greatly reduced. So that’s suggesting a link to pink salmon.”

Ruggerone added that the potential impact of pink salmon abundance is also a concern for Fraser River sockeye.

“In their second year, they start competing with these super highly abundant pink salmon,” he said.

Greg Taylor, a fisheries adviser for Skeena Wild Conservation Trust and Watershed Watch, said a growing body of evidence showing a link between commercial-scale hatcheries and wild salmon is getting harder to ignore.

“I think the science is compelling,” he said. “The logic is compelling. And it’s hard to deny. I don’t think there are any people experienced in the salmon world who would argue against this concept.

“In the context of climate change … we see vast changes to the North Pacific, and at the same time we’re pumping out increasing numbers of hatchery fish. And it’s making it very difficult for wild populations. And, in specific, there’s concerns over chinook.”

Taylor fears that the success of hatcheries in boosting pink and chum salmon abundance might be used as an argument to ramp up hatchery production of species that are in decline, such as chinook, coho and steelhead.

“To me, this is akin to advocating for more coal-fired power plants to run air conditioners to combat the effects of climate change,” Taylor said. “It addresses a symptom while exacerbating the problem.”

Irvine and Ruggerone conclude their study with a recommendation that Alaskan fisheries managers implement tagging and genetic stock identification of hatchery fish so that when commercial fishermen catch the fish, they will know if the salmon are “natural origin” or from hatcheries.

Asked if that is something Alaska would consider, Swanton said: “I would contend that there ought to be large-scale tagging of chinook. By and large, there’s a lot of information that could be extracted from that.”

nbennett@biv.com
@nbennett_biv

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