In the American Northwest, the struggle to save endangered runs of salmon is one of the epic crusades of the contemporary conservation movement. Seventeen strains of Pacific salmon are currently listed as threatened or endangered. Two more are labeled “species of concern,” meaning they are close to jumping onto the list.
So what are we to make of this: A recent study published in the journal Marine and Coastal Fisheries found that the north Pacific Ocean may be nearing the limit of its salmon-carrying capacity. The North Pacific is becoming “overcrowded with salmon,” according to Randall Peterman, one of the study’s authors and holder of the Canada Research Chair in Fisheries Risk Assessment and Management at Simon Fraser University in Vancouver, B.C. He and his co-author, Seattle-based fisheries biologist Greg Ruggerone, recently set out to compile the most complete set of data on Pacific salmon abundance. What they found is that today’s total Pacific salmon population is twice what it was 50 years ago. “We’re seeing more total salmon now than we’ve ever seen before,” says Peterman.
A surprising number of those fish — more than one in five — originate in hatcheries. And that has created its own set of problems. Masses of
In 1970, hatcheries released 500 million young salmon. By 2008, that figure had jumped to 5 billion.hatchery-bred salmon are gobbling up smaller fish, krill, and other prey, reducing food supplies in the North Pacific for endangered wild runs and hampering their recovery. In addition, hatchery fish, which come from limited brood stock with less diverse DNA, aren’t as genetically fit as wild salmon to support the long-term survival of the species.
How can numerous Pacific salmon runs be on the verge of extinction while total salmon numbers are straining the limits of the ocean’s capacity to support them?
According to the researchers, the abundance of some salmon species has been caused by a resurgence in wild salmon populations due to productive ocean conditions, as well as to the ever-increasing production of hatchery fish. But the problem is, the resurgence of wild populations hasn’t been universal. Five species of salmon exist in the Pacific: Pink, chum, sockeye, coho, and Chinook. (The Atlantic Ocean has only one species, the Atlantic salmon.) Over the past quarter-century, pink salmon populations from around the Pacific Rim have doubled, thanks, in part, to hatchery production. Other runs, such as Upper Columbia River Chinook and Snake River sockeye, limp along in alarmingly low numbers.
The triumph of industrial salmon hatcheries is written in the numbers. Between 1970 and the late 1980s, the U.S., Canada, and their Pacific Rim neighbors ramped up their hatchery programs and pumped out vast numbers of young salmon. In 1970, hatcheries released around 500 million young salmon into the Pacific. By 2008 (the last year for which data is available), that figure had jumped ten-fold, to 5 billion.
Most of those hatchery fish — about 90 percent — were pink or chum, the most common of the five species of Pacific salmon. Japanese hatcheries pump so many chum salmon into the Pacific that hatchery chum have outnumbered wild chum since the mid-1980s. One-third of Alaska’s 2010 statewide salmon harvest originated from five hatcheries in the Prince William Sound/Copper River region.
(Hatchery-bred Pacific salmon are raised in industrial facilities from eggs and then released as fry into rivers and flushed out to sea with the spring freshets. They are not the same as farm-raised Atlantic salmon, which live out their lives in net pens.)
That flood of hatchery salmon entered the ocean during an auspicious time. Every 30 years or so the Pacific undergoes a regime change,
Young salmon enter a fierce competition for finite food resources in the North Pacific.switching from an era of colder water temperatures to warmer ones, and then back again. It’s called the Pacific Decadal Oscillation. Around 1978, the ocean switched from a colder period to a warmer one. (We may now be switching back to a period of cooling, partially offset by the effects of global warming.) That warming boosted the production of phytoplankton, which in turn increased populations of the tiny crustaceans and juvenile fish that salmon feed on.
Put simply, after 1978 there was a lot more salmon food in the ocean. The total number of adult salmon in the North Pacific jumped from roughly 300 million in the 1952-1975 period to nearly 650 million in the 1978-2005 period. Of those 650 million adult salmon, the commercial fishing industry harvests about half. (What happens to those 5 billion hatchery fry? Like their wild counterparts, most get eaten before coming of age.)
The salmon prey buffet is not unlimited, though. When young salmon from around the Pacific Rim leave their rivers, they enter a fierce competition for finite food resources in the great mixing chamber that is the North Pacific. Greg Ruggerone’s previous research found that there are winners and losers out there — and those results may have profound implications for hatchery management, international fisheries agreements, and the future of Pacific salmon.
The winners? Pink salmon. “Pinks are interesting because they’re the smallest and shortest-lived of the salmon species,” Ruggerone told me recently in his office near Fishermen’s Terminal in Seattle, home port for much of America’s North Pacific commercial fishing fleet. “And yet they’re the dominant competitor in the ocean, and the most abundant Pacific salmon species.”
Much of their success lies in the pinks’ two-year life cycle. Young pink salmon hatch in the early spring of an even-numbered year, overwinter in the ocean, then return to spawn — usually in the lower reaches of coastal rivers — in the autumn of the following odd-numbered year. “They have to grow very fast, so they’re programmed to eat lots of food,” says Ruggerone.
Other species have longer, more complicated life cycles. Sockeye salmon typically spawn in or near lakes. They live in freshwater for their first two years, then spend two years in the ocean before making the journey back to
It’s no coincidence that most threatened salmon species are in the West’s most industrialized river systems.the spawning lake. That journey to and from the lake can be epic. One run of sockeye spawns in Redfish Lake, Idaho — 900 miles from the Pacific. Chinook and coho also spend a lot of their lives in rivers, where they’re susceptible to the wear and tear of dams, industrial pollution, high temperatures, low oxygen, and a sketchier food supply caused by loss of habitat. It’s no coincidence that a majority of the federally listed threatened or endangered Pacific salmon species are Chinook, coho, sockeye, and chum that spend at least part of their lives in two of the West’s most industrialized water systems, Puget Sound and the Columbia River.
Pinks, by contrast, are built for 21st century reproductive success: Dash to the ocean, avoid the human-based threats in the river, eat like fiends, then make the short sprint home to spawn. Pink salmon are conspicuous by their absence from the endangered species list.
And they’re only expected to widen the gap. As climate change forces a warming of marine temperatures, spring phytoplankton blooms — which lead to a boom in zooplankton, aka salmon food — come earlier, which benefits the pinks. Pink salmon are typically the first salmon to enter salt water in spring, ahead of the other salmon species. In Puget Sound, for instance, the peak plankton blooms are arriving earlier. “By the time Chinook salmon reach the sound in June,” says Ruggerone, “there’s less food available because the peak plankton bloom has come and gone. And the pink salmon have already eaten much of it.”
So even before they move from Puget Sound into the open ocean, the pinks are well fed and strong, Chinooks less so. When pinks compete with other salmon for food, pinks win.
Consider this contest: pinks vs. sockeye. Every year more than 1.4 billion hatchery pinks are flushed into the ocean, mostly from the Russian Far
All of this wouldn’t be a worry if hatchery salmon were the equal of wild salmon. But they’re not. Until recently, most hatchery salmon came from a small pool of eggs, with little thought given to matching hatchery runs with broodstock from their river of origin. The genius of the salmon species, of course, lies within their diverse DNA, with each run exquisitely adapted to the conditions of its home river. Hatchery fish, for the most part, have dumber DNA. And the advantage hatchery pinks have over wild runs of other salmon species is only expected to increase as ocean temperatures rise as a result of climate change.
In a controversial study, University of Washington fisheries professor Ray Hilborn and Alaska Department of Fish and Game biologist Doug Eggers
‘We’re seeing very clear signs that the north Pacific Ocean is reaching its limit for salmon,’ says a researcher.published research suggesting that hatcheries played little part in Alaska’s great pink salmon boom. The state’s commercial pink salmon catch grew from 3 million fish in the 1970s to more than 20 million in the 1980s, after the installation of industrial hatcheries, and the boom is popularly attributed to the hatcheries. Hilborn and Eggers argued, however, that the same boom would have happened without the hatcheries because of more favorable ocean conditions — and those runs would have been wild, not tank-raised.
“What we did with hatcheries was take a free way of making fish, and turn it into an expensive way of making fish,” Hilborn told me.
The implications of the research by Hilborn, Peterson, Ruggerone, and others is starting to affect policy decisions. Over the past decade, a wave of hatchery reform — designed to help wild runs, rather than hurt them — has swept through the industry in Washington State. In Alaska, state regulators are starting to push back. Earlier this year the Prince William Sound Aquaculture Corporation, one of the world’s largest salmon hatchery operators, asked permission to release an additional 95 million pink salmon fry. The Alaska Department of Fish and Game denied the request — a rare refusal of the politically powerful fishing industry. The state wanted to safeguard wild salmon runs against genetic mixing with the hatchery stocks, and was concerned that the increase might push the North Pacific to a tipping point. (The state did approve increases in the company’s chum and sockeye releases.)
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So for now, hatcheries will continue to pump more and more salmon into the system. “Ecosystems have limits,” says Ray Hilborn. “And we’re seeing very clear signs that the north Pacific Ocean is reaching its limit for salmon.”