Saving salmon means spreading risks among diverse populations, important new study says

Saving imperlied salmon in the Pacific Northwest means focusing a lot more on the genetic quality of the fish and a lot less on the quantity of fish cranked out in hatcheries, suggest the authors of a groundbreaking new study in the prestigious science journal Nature.

The notion that spawning lots of salmon in hatcheries could actually impede efforts to bring back struggling wild runs is not a new one. The science on that is solid. But the new study, which focused on the success of salmon runs in Alaska’s hatchery-less Bristol Bay, is “a game-changer,” according to the University of Washington team that produced the research.

Here’s why: The new study documents how Bristol Bay for more than half a century has consistently produced fishable sockeye salmon runs. That’s because in a natural system like Western Alaska, the existence of so many different runs that reproduce in different nooks and crannies of the ecosystem ensures that – whatever happens – some salmon runs will thrive. Runs that do well in cold, wet years are winners sometimes. Other times, when temperature and rainfall are relatively mild, runs better suited to those conditions will boom.

But every year, at least some runs will do well. It’s all about spreading out the risk.

Think of the varied salmon runs of Bristol Bay like a financial portfolio well-positioned to endure whatever goes down on Wall Street: stocks that take advantage of upturns, bonds that hold value in down times and maybe some real estate or pig belly futures or gold bullion thrown in for good measure.

In fact, the researchers called this spreading of the risk “the portfolio effect.” Author and UW fisheries researcher Ray Hilborn ran with that financial analogy, saying maintaining diverse salmon populations is akin to holding a variety of investments.

 “Anyone who put all their money on the ‘hot stock’ – be it Enron or the Florida real-estate market – learned that lesson,” Hilborn said.

Each salmon hatchery literally puts all of its eggs in one basket – a really big basket that’s filled with water. The fish become more genetically similar as time goes on. The young fish are also typically all released at once, and return to spawn at about the same time. If a disaster occurs at that particular time – a drought that leaves the water lethally warm for salmon, for example – a huge part of the run doesn’t make it back to reproduce.

Or consider how in the wild, different salmon head to sea at different times of the year. Their arrival is ideally timed to when spring weather encourages a burst of biological productivity – lots of food for young fish. However, the timing of that burst of food can vary. Sometimes it could come as early as April, other times as late as July. Because so much genetic diversity is preserved in Bristol Bay fish, some will hit the ocean in every month from mid-spring to early summer, ensuring that at least some will survive to return and spawn.

The Bristol Bay sockeye salmon run is important in its own right. From 1950 to 2008 sockeye salmon represented the largest fishery in the country – some $7.8 billion worth was caught – and Bristol Bay sockeye made up nearly two-thirds of that. The new study points out that the diversity of salmon runs entering Bristol Bay is the lynchpin of the region’s economy, which is based largely on salmon fishing. 

But the implications stretch far beyond Bristol Bay or even Alaska, said fisheries researcher Jeff Hutchings of Dalhousie University in eastern Canada, who formerly was chairman of the Canadian government’s Committee on the Status of Endangered Wildlife. He called the new study “groundbreaking.” 

“It’s the first empirical evidence I’m aware of at such a large economic scale of the fundamental importance of preserving variability in (wildlife) populations,” Hutchings said. “Whether it’s fish or plants or mammals or whatever, (the new study) is identifying the importance of variability that perhaps hasn’t been as fully appreciated before.” 

Steve Lindley, a National Marine Fisheries Service research ecologist, said the lesson to him is: “We do need to be changing the game from hatcheries, the quick technological fix. That’s what we’ve been pursuing for the last 50 or 100 years, and it’s not working.

“It means we have to fix it. There probably aren’t any super-easy shortcuts like fish hatcheries. We need to get back to working on the habitat.”

The study was featured on the cover of Nature this week. UW researcher Daniel Schindler, the lead author, compared the runs in the Lower 48 with those of Bristol Bay by using an analogy to lottery tickets. 

The young Bristol Bay sockeye head into the ocean over a period of months because of genetic differences in the runs, and genetic differences among individual fish within a run. 

But the embattled Sacramento River chinook, whose genetic diversity has been reduced through hatcheries, dams and other features of modern life, all head to sea within a period of a few weeks. If they hit a food-short ocean – which can happen for any number of reasons, many related to climate – that year’s class of salmon will be decimated. 

“Down in Sacramento, they’re buying one or two lottery tickets,” he said. “In (Alaska), they’re buying lots of lottery tickets.” 

Running simulations of what would happen if the California genetic situation were superimposed on even the healthy Bristol Bay watershed of Wood River, the UW scientists found that Bristol Bay fishermen would have had to sit out every second or third season over the last half-century. Instead, the last time the fishery was closed was 1973. 

Bad years for Sacramento River salmon, on the other hand, led to the largest closure of West coast salmon fisheries in history in 2008 and 2009. 

In the Lower 48, the arrival of modern civilization translated to the disappearance of 29 percent of some 1,400 locally adapted salmon runs, the scientists found. Putting the researchers’ advice to work in the Pacific Northwest is a lot harder than it sounds, said Steve Parker, a fisheries biologist with the Yakama Nation Indian tribe in Eastern Washington who has experience working on Bristol Bay salmon. 

“We get these blue-ribbon science guys who have absolutely no experience grappling with the actual management problems, and they make these scientific pronouncements as if they’re the first one to think of it, and it rankles me,” Parker said. “I know some of those guys and respect them, but they are not working on the problems on the ground.” 

Of course it would be better to have preserved more genetic diversity in salmon in the Columbia Basin, Parker said, adding that he agrees with the study’s conclusions. But dams, farms that draw water from the river and other modern facts of life have tied salmon managers’ hands and forced them to rely on hatcheries, he said. 

For example, only one fifth of the Chinook that return to the Columbia River in the spring are wild fish. The other 80 percent – the bulk of the catch, by far – come from hatcheries. Parker asks: Where would people get spring Chinook if the hatcheries closed? The wild runs. Would that be good for the wild runs? No, it would not. 

“That’s what this portfolio effect is: risk spreading among populations,” Parker said. “We’d love to be able to do that in the Columbia Basin. Unfortunately, decisions have been made and continue to be made that steadily and continuously and I think it could be argued continue to take away opportunities to spread the risk.”

 “Now the question is for the region is: How much do you want to work back in the other direction? What are you willing to liquidate in your existing portfolio to help salmon stocks? And  is that even still possible?”

 The UW study was financed and co-authored by the Gordon and Betty Moore Foundation, a California-based philanthropic fund dedicated to environmental conservation and scientific research.

 — Robert McClure