Sockeye Feel the Heat
Global warming cranks up stress on salmon. Scientists are scrambling to identify what the heat's unleashed. Second in a two-part series.
[Editor's note: As the Cohen Commission reconvenes this week to investigate the fate of B.C's fragile sockeye population, we bring you the second of two excerpts from Jude Isabella's soon-to-be-published Salmon: A Scientific Memoir, a science writer's look at the relationship between salmon and humans. Included in this article is the subject taken up by the Cohen Commission today: Whether a virus is putting B.C.'s sockeye salmon population at dire risk.]
Scott Hinch has studied sockeye for almost 20 years and he's still amazed when an elegant study reveals something new. A University of Toronto graduate, Hinch focused on warm-water fish in Ontario lakes before migrating towards salmon and a chance to live in British Columbia. Today he helps oversee many research projects attempting to discover what threatens the province's sockeye populations, and how to help salmon become more resilient.
What Hinch worries about most when it comes to salmon are two horsemen of the environmental apocalypse: warming temperatures and pathogens.
The Fraser River is close to 2 C warmer than it was just 50 years ago for cold-blooded salmon. That's a problem.
"Warmer temperatures are going to be a big influence on disease proliferation so I'm very interested and concerned about that angle and we know so little," he said. "The research hasn't been done."
All sorts of circumstances drive pathogens -- infectious agents such as viruses, bacteria, fungi, and prions (a cause of the fatal brain disease BSE) -- to morph or spread. Crowded fish farms in Chile, for example, hastened the spread of the infectious salmon anaemia virus. And climate change is a big player in pathogen behaviour. So given the almost slam-dunk certainty that Earth will be warmer in our lifetime, what can sockeye expect?
A study by DFO scientist Kristina Miller, who is slated to testify to the Cohen Commission today, is a worrisome foreshadowing of things to come. Miller's study, co-authored by Hinch, Farrell, Cooke and other scientists, exposed a possible disease killing Fraser River sockeye before they get a chance to spawn. Referred to as "salmon leukemia," it is potentially the culprit behind falling salmon numbers over two decades, culminating with the 2009 collapse when only a million fish came back out of an expected 10 million.
Sockeye salmon's immune systems are compromised and it's possibly a virus at play. Scientists don't know how it's transmitted, whether from parents to offpsring or fish to fish and whether it's endemic to all fish or only to salmon. They're not sure if it's related to climate change or the role of other stressors. What they do know is if a fish has the signature of this possible virus, the fish is most vulnerable to sickness when morphing itself physiologically to make the switch from saltwater to freshwater. The possible virus could be the driver behind a fatal behaviour change: late-run sockeye that migrate in early autumn when temperatures are cooler have developed a timing issue. Since about 1996, they've been migrating anywhere from three to eight weeks earlier than historically normal making them more vulnerable to the disease under study. Late-runs that show up early to spawning grounds are more likely to die before they can reproduce.
A doctoral student co-supervised by Hinch and Miller might soon yield answers about the possible virus. He is analyzing data on the cellular response of artificially heated sockeye and pink salmon. Some of the sockeye in the study have the possible viral signature. Any temperature-related disease progression may be detectable in them.
A parasite called Ich
Rising temperatures have already been blamed for the Ichthyophonus parasite that, since the 1980s, has been infecting and killing Yukon River chinook salmon. The river is almost 6 C warmer than it was over 30 years ago. "Ich" (appropriately pronounced "ick") was thought to be a fungus at first and the state of Alaska dragged its feet in addressing the problem. It took independent research to convince Alaskan fisheries officials that in warm years Ich was infecting almost half the Yukon River female chinooks. Peak infection was in 2003-2004. Infection and disease has steadily declined, to four per cent. But Yukon River chinook numbers have declined too -- by 60 per cent, from 268,537 in 2003 to just 107,000 this year.
Not all chinook are likely equally susceptible to Ich. Lab tests showed some B.C. chinook populations might be less susceptible than Yukon River chinook. In Washington State's Puget Sound, the chinook have very low levels of Ich, even though they feed on heavily infected herring. They'll also resist infection from a Yukon River parasite if introduced. Without population diversity, chinook might not fend off the disease. It fits into the idea of the "portfolio effect" as described by University of Washington scientists last year. They took over 50 years worth of research on sockeye salmon from Bristol Bay, Alaska -- the largest sockeye fishery -- and showed that the genetic diversity of its sockeye populations gave the fishery stability. Just as a diverse financial portfolio ensures financial stability as markets go up and down, a diverse genetic portfolio gives the biological system stability.
Heating up the food
There's another reason water temperature is such an important variable when it comes to studying the fate of B.C.'s sockeye -- a growing fish has got to eat.
Sockeye salmon generally swim up the Fraser River in their fourth year. They lay eggs, die, and in spring the fry emerge. Most head for a lake, probably to avoid predation. When a fry emerges it's only about the length of an inch worm, a perfect snack for a bigger fish. To a young salmon, the ocean would hold the same attraction as a buffet does for a growing human adolescent, but sockeye fry must opt for leaner rations. In food-poor lakes they have less to eat, but they're also less likely to end up as lunch. A trade-off -- food availability versus predation -- and no doubt a good evolutionary move.
To find the lake, fry rely on either the sun's position or polarized light patterns. Put fry in a covered round tank to deny them visual cues as well as odours and a water current, rotate the magnetic field with a direct electrical current, and they will navigate by Earth's magnetic field. The sensory-deprived fish head in the direction they normally would to their home lake. One of B.C.'s largest sockeye populations, Chilko River fry, for example, will orient south since they enter Chilko Lake's north end.
Fry have two things to do in the lake: eat and avoid being eaten. The good news for sockeye is that they're usually the most abundant fish feeding on tiny crustaceans. The bad news is that just like the adults that come back to spawn, temperature matters. When food is plentiful, fry grow best at 15 C. Lower the temperature and it takes longer to digest food. Raise the temperature and the fry's metabolism kicks into high gear so that food barely maintains the fish. If food is less plentiful, the fish needs lower temperatures for best growth.
Of course, sockeye nursery lakes vary in temperature, elevation, and geography and individual populations will vary in their adaptive responses, just as humans do in their varied habitats. Andeans, Tibetans and Ethiopians living at altitudes above 2,500 metres have three different biological adaptations to oxygen-thin air. The Andeans have more hemoglobin, the oxygen deliverer, in their blood. Andeans can breathe at the same rate as a person living at sea level, yet move more oxygen around the body. Compared with sea-level people, Tibetans take more breathes per minute. They also might use another gas, nitric oxide, more efficiently, which widens blood vessels allowing more blood to flow. The Ethiopian adaptation is different but remains a mystery for the moment.
Humans that adapted to higher elevations likely did it culturally first, through the use of fire and warm clothing. They had time for biology to catch up. Other animals lack that luxury and salmon have the added complication of living in multiple habitats. They move from freshwater to ocean to freshwater again and have wildly different needs at different life stages. Food, for example, is not a need at all once they start their final migration to spawn but this means they have a lot of eating to do before starting up river. They gain 90 per cent of their biomass in the ocean.
The inescapable human factor
So how would you fix declining sockeye runs in British Columbia, I asked one population geneticist. His answer was simple. "Probably just fix their habitats and leave them alone."
Unfortunately for salmon, especially the sockeye in the Fraser River watershed, habitat is more than a scientific concern. It's a commodity, which means people are not likely to leave them alone. The Fraser River is home to over 100 sockeye populations with a commercial worth of over $1 billion annually, on average. Canada's commercial relationship with the fish is older than the scientific relationship. Since the Hudson Bay Company began exporting salted salmon in cedar barrels from Fort Langley on the Fraser River in the 1840s, the numbers of people invested in sockeye has climbed, while sockeye numbers have declined.
In yesterday's article in this two-part series, I introduced you to "salmon doctors" who catch, test, and perform surgery on fish along a super productive stretch of the Harrison River they call "The Park." Those scientists are -- on a wider scale -- conducting studies about us. By studying the aging process in fish, for example, it tells us something about the human aging process. On a practical level, the science gives fisheries managers much needed information. Maybe, eventually, the data will affect policies. But once they release it, scientists know they have little, if any, control.
"We all know, from the cod collapse on the East Coast, that even some of the best science can be ignored," says scientist Hinch.
"I don't think there's any pattern. I think it really depends on the local situation and the people who are involved. History has shown us that in other fisheries small studies can provide really unique information, that if the right people see it and understand it, they can act on it quickly."
History -- going back thousands of years -- is another potential trove of insights about how to save the sockeye salmon. Like most places fished today in B.C., The Park is within a traditional use area of First Nations. The aboriginal peoples fished here for thousands of years. They're known, in recent centuries, as the Coast Salish, a group bound by language and culture inhabitating communities stretching from the Lower Mainland to Vancouver Island and Washington State. The Sts'ailes, the fishers that run the beach seine for the studies, are Coast Salish. Archaeologists have found settlements on both banks of the Harrison River and on mid-river islands, all built within 50 metres of the river or sloughs. Settlement dates remain unclear but it's safe to say human occupation of The Park is ancient.
Humans have lived along the rugged, fjord-riddled coast of B.C. for at least 11,000 years. They've coralled fish to their doom with nettle-fibre nets, stones traps, and wooden weirs. The evidence is there, from California to Alaska, even on rivers and streams that no longer host salmon runs. (Remnants of a wooden weir were still visible in the 1970s at Morris Creek, a few kilometres upstream from The Park.) Archaeologists believe that the size of the runs of salmon was less important to early peoples than was access to many populations, big and small. It's possible that the clues to sustainable management lie in the past.
Unearthing answers will take cooperation between scientific disciplines -- a real challenge when it comes to combining biology and anthropology. They generally tend to have different mindsets. For biologists to infer a conclusion -- for example, with studies about fish farms' effect on wild salmon -- makes them suspect as scientists. In anthropology, studies that infer can lead to audacious and yet acceptable conclusions about humanity (even by biologists.) For example, studies that infer humans consistently destroy their environments are often treated as conclusive evidence that as a species we are incapable of conservation. It stems from a desire for a tidy theory of human behaviour from an objective scientific standpoint. It's an unobtainable goal.
Charles Darwin's breakthrough -- evolution by natural selection -- gave biology the grammar to move forward as a science. It gave anthropologists grammar, and a headache, for the last 150 years. Both biology and culture help to explain human behaviour, and the challenge remains in keeping them complementary yet separate. We're all the same, and we're all different -- and that's the starting point. As a species we have the same biological needs, how we meet them will differ. Our culture believes every human culture will eventually destroy itself because it's easier to find evidence of past environmental destruction. We haven't been looking for evidence of conservation and until recently, we didn't even know what it might look like.
Another day in The Park
At 4 p.m. the buzz of activity is muted at The Park. The fishers are packing their gear and the catch at the lab tents is dwindling. A warm breeze carries a sweet, hay-like smell from the grassy riverbank to overlay the odour of blood wafting from Wilson's fish morgue. She has placed 28 salmon brains in vials today, for transport and later study. I imagine a FedEx delivery to the wrong doorstep, someone expecting smoked wild sockeye fillets, not teeny, raw fish brains.
At the surgery table, scientist Tim Clark continues with his scalpel at a feverish pace. "It's a girl," he calls out at one point incising a belly with quick strokes. The data logger he inserts into the fish to monitor heart rate and other stress indicators is encased in the same silicone used in biomedical implants for humans. Clark often adapts for his fish studies the tools of medical doctors. At the Cultus Lake lab, he has a meter originally intended to measure hemoglobin levels in human blood, which he recalibrated for fish blood, and he adapted a glucose counter for diabetics to count fish glucose levels.
The implant he has just inserted in the female sockeye will rest against her organs, and the tiny computer inside it will record internal temperature as well as electrical pulses from the heart. Once patched together, she'll go to a temporary pen in the river for a few hours before she's let loose to find her natal stream. Not a single fish of Clark's has died since I arrived.
In a few weeks, Clark will go to Weaver Creek to find his tagged fish to remove the computers. The data should tell him if the Weaver fish look for the cool spots in rivers -- thermal refuges -- to save energy, and how the fish allocates what energy it has during migration . "No one really knows that," Clark says.