They do heart surgery on sockeye, splash fish to test stress, and more -- all to unlock vital secrets of survival. Part one of two.
'Fish chasers' splash salmon captive in pools to measure their resilience to stress. Photo: Jude Isabella.
[Editor's note: As the Cohen commission reconvenes this week to investigate the fate of B.C's fragile sockeye population, we bring you 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. Today: The biological detectives researching what makes salmon resilient -- or not.]
It's drizzly, cold, and muddy, and a folding table on the south bank of the Harrison River is no place to perform open-heart surgery. Tim Clark has just begun. He quickly focuses on his delicate patient, who is sucking in anesthetics through a tube down the throat. Clark stares at the body and his tongue sticks out in concentration as he leans over. The patient's flesh is slippery, but he slices deftly into the chest cavity. In minutes, he has stitched up the wound and handed off the patient to be taken away, slightly groggy but still kicking.
The van full of medical supplies behind Clark -- gauze, forceps, gloves -- is a MASH unit without a war. To the sockeye salmon resting on the operating table (a Rubbermaid container) the process must seem more like an alien abduction than surgery. Clark is no alien, though he is Australian. His purpose is to insert a data logger into the cavity behind the gills and near the fish's heart. A tiny computer will record heart rate and temperature once the fish is released back to the Harrison River and during its final sprint to Weaver Creek, the natal stream where this population of sockeye will spawn before dying. Each surgery takes 10 to 15 minutes, depending on the fish's sex; male salmon have thicker ventral tissue and need fewer stitches to close the opening.
Clark and the rest of the scientists arrived early this morning, in the cold mist of sunrise. Swaddled in fleece, raingear and chest waders, they set up tents, tables, scalpels and tubes, then waited for the fish. The fishers, men from the Sts'ailes (formerly Chehalis) First Nation's fishery program, are running the beach seine to catch patients for Clark and his colleagues, and it's high drama to watch them pull it off. They fix one end to a truck on shore, the other to a motorboat that zooms across the river and loops back to shore, snaring the catch. From dawn until about 4 p.m., they'll deploy the seine net eight times, catching fewer salmon as the rain stops, the sun shines, the day warms, and the fish sink deeper into cooler water. The scientists have partnered with the Sts'ailes fishers for the past six years, the fishers taking DNA samples for their own fisheries program, the scientists inserting monitors. In most ways, the operations feels a lot like a traditional fish camp -- except that the salmon give up their bodies for data, not food.
Knowing nothing of seining, I jumped in with everyone else to help pull in the nets full of salmon. Being on the small side, I was the weak link in the tug-of-war. The fish slapped my legs, thrashing and catching their teeth in the netting. Standing there in the midst of them gives a sense of how powerful salmon need to be to swim against the river's current. It was easier to help Clark and a couple of graduate students make the transfer to the operating room's waiting area, scooping salmon in hand-held nets and wading through the water to plop them into a pen. I stood in the water and wrote down tag numbers as they evaluated each fish, plucking off a scale to send to a Department of Fisheries and Oceans temporary lab at Weaver Creek.
Sockeye populations can be identified by scale patterns viewed under a microscope. Within an hour of sending the first catch, the lab, set up just for this purpose, called Clark to tell him that 11 out of the 25 were Weavers; the rest were Harrison River fish. The distinction matters. Clark studies compare fish physiology between salmon species and populations within the sockeye species. The focus of this study was Weaver sockeye, not the more plentiful Harrison sockeye. Clark pulled on his surgical gloves to start cutting.
Humans have known, through observation in the ancient past and through experimental science today, that the more salmon runs there are, the healthier the species is overall. Whatever challenges salmon face -- climate change, disease, industrial pollution, overfishing, hatchery production, fish farms -- they will ultimately evolve or go extinct depending on their diversity. Yet scientists are forced to prove over and over again, in deepening detail, that a species is doomed without population diversity, especially as the climate changes and water warms. The work these scientists do shows the fine, unseen, differences between sockeye populations. It should be simple. But it isn't simple because our relationship with sockeye is overwhelmingly about money. There is nothing simple about money.
Slippery surgery: Tim Clark inserts data logger into salmon before releasing the fish back into the wild. Photo: Jude Isabella.
Super productive Salmon Central
The 150-metre stretch of land along the Harrison River where scientists conduct fieldwork belongs to the Sts'ailes First Nation and is called simply "The Park." Roughly five kilometres from the Fraser River, it's one of the most productive fish habitats in the Fraser Valley.
All five Pacific salmon (pink, chum, chinook, coho, and sockeye) species swim these waters, traditionally running from June to March. Even today, after years of commercial fishing, logging, and industrial pollution, the ecosystem erupts with life. The fish attract loads of birds. In the next couple of weeks the Park will swarm with teals and other ducks, the Sts'ailes fishers tell me, adding that over the past six or seven years cormorants have made a big splash in the area gobbling any fish that fits into their bills, including a two-pound trout. An occasional sea lion has been glimpsed trolling the Park having travelled 150 kilometres from the sea.
The riverside heart surgery is one of many in-depth sockeye studies. Fish biologists Scott Hinch and Tony Farrell at the University of British Columbia in Vancouver and Steve Cooke at Carleton University in Ottawa manage most of them. Lift the lid on their research and it's like picking up a patio stone and seeing a colony of ants at work, all frantically moving toward individual goals that converge on a single purpose: to understand the physiology of salmon in excruciating detail. No function seems to go unnoticed, from heart rates and temperature tolerance to aging.
A few strides away from Clark's station, one of the younger team members stands under a tent and eviscerates dead sockeye, plucking out brains and hearts. Samantha (Sam) Wilson flash-freezes the organs in liquid nitrogen and stores them in a cooler to be couriered overnight to Ontario. Wilson, an undergraduate student at Carleton University is intrigued by a question of colour. She wants to know if brighter-coloured salmon age more slowly than dull-coloured salmon. A salmon's bright-coloured skin comes from caritinoids (antioxidants) from the food they eat. It's possible that brighter-coloured salmon (having higher antioxidant capacity) are better at preventing aging and survive longer on spawning grounds. If so, do they pass this antioxidant capacity to their offspring? The question arose from studies showing that birds with bright-coloured beaks tend to have higher antioxidatant capacity than birds with dulled-coloured beaks.
Wilson expertly cuts into a fish brought to the operating table by Graham Raby, who is charged with giving Wilson fresh kill. Raby, a graduate student at Carleton, evaluates Fraser Boxes, plywood boxes through which freshwater runs to revive fish nabbed as bycatch by commercial fishers -- the boxes are painted black to soothe the fish -- and fish bags, which are essentially black duffle bags with mesh at each end. The bags are a low-tech method for reviving fish caught by sport fishers, something they're not required to use, yet. When Raby is done reviving the fish, he bonks them on the head and brings them to Wilson. The salmon is slippery and strong enough to launch a heavy lid off the Fraser Box, so Raby has weighted the boxes with large rocks. Holding down a sockeye and administering a deadly blow on the first swing is tough. Raby is quick and efficient, though. He disappears down a short trail that leads to the river and the Fraser Boxes to continue his work.
Graham Raby collects a salmon specimen whose heart and brains will be harvested for study. Photo: Jude Isabella.
Who's best under stress?
For the past 10 years this group has focused mostly on stress physiology and the effects of temperature, particularly of warming waters. The conclusion, so far, is what one might expect: Fish that experience high temperatures naturally are better at coping with stressors under high temperatures. Fish that experience cooler temperatures naturally cope less well with stressors when rivers warm. It's a bit like comparing Vancouverites on a 30-degree C day with little humidity to visiting Torontonians. The Vancouverites are wilting, while the Torontonians are delighted to have escaped the oppressive heat and humdity back home. Although it's not quite the same: we warm-blooded humans can handle it even if we don't like it. Cold-blooded salmon can't.
Erika Eliason, who does similar fish physiology work to Clark's, is at the DFO lab at Cultus Lake, about an hour drive east of Vancouver. She sits on an old couch in a bungalow the students share as they spend long summer days on various fish studies. Close to the house, freshwater pools dot a fenced, concrete area. Chasers, graduate students, take turns using their arms to churn the waters of a pool where an adult sockeye swims, having been caught from the lower Fraser River just a few days previously. To chase fish, you need a stopwatch, knee pads, and lots of energy, particularly if it's a hot day. Four women flail their arms in a pool as another watches, a stopwatch in one hand and a clipboard in the other, and calls out encouragement. After three minutes of chasing, the fish is held in the air to simulate what happens when it's caught. The stressed fish are then placed in other pools at temperatures ranging from an ideal 16-degrees Celsius to a worrisome 21-degrees and their stress levels are monitored. The group will do this for 120 fish. Like the fieldwork, a couple of questions are in play: how well do stressed fish recover, does temperature matter to recovery, and whether handling them revs the aging process, making them less likely to reach their spawning grounds.
Eliason is cruising toward the conclusion of her PhD and is there to help fellow students with whatever needs doing, like chasing fish or teaching fish surgery. I had 20 minutes to interview her, which was perfect, like sitting through a private TED Talk. Eliason could make an eight-year-old care more about Fraser River fish distinctions than the supernatural powers of superheroes.
"These fish are adapted to their environments, which is really interesting in a lot of different ways," Eliason said. "And if you think about it, it's such a narrow part of their lives -- only four weeks, three weeks, or two weeks of migrating, but clearly this is a very critical part of their lives."
In general, migrating sockeye suffer when temperatures are above 18-degrees Celsius. And if things get too warm, some populations are likely to die of heart failure during their heroic journeys to reproduce. Weaver sockeye, which travel a mere 150 kilometres or so to spawn, are the skinny weaklings on the beach compared with Chilko sockeye that travel 650 kilometres to spawn further up the Fraser River.
Catching sockeye salmon by seine net for study on the Harrison River. Photo: Jude Isabella.
It took three years for Eliason to figure this out. She spent many evenings inserting catheters into sockeye from various Fraser River populations and taking blood samples as they swam in freshwater pumped into big swimming tunnels made from PVC piping at the Cultus Lake lab. The goal was to compare how well they took up oxygen from the water at rest and while swimming -- the "aerobic scope" -- to feed their muscles, how well they pumped blood around their bodies, and heart size. As she monitored the fish, she also tweaked the water temperatures.
The names of Eliason's sockeye populations evoke the settlers and First Nations meeting along the Fraser River: Early Stuart, Nechako, Quesnel, Chilko, Lower Adams, Weaver and Gates. The powers of the populations are as diverse as the people who could wrest a fortune, or not, from the mighty Fraser. The Chilko are the Lance Armstrongs of the group, physiological freaks with big hearts, incredible oxygen uptake, and an ability to swim powerully up to 22-degrees Celsius, losing steam after that but still moving at 26 degrees. They migrate into warm summer waters, then cruise through glacier-fed rivers to spawn. They can handle the cold and heat. Nechako migrate over 800 kilometres, but in water without temperature extremes: heat the water up to 20-degrees Celsius and they stop swimming. They have the aerobic scope but not the heart of the Chilko. The Weaver, the weakling, has neither. Compared with the mighty Chilko -- historically about a quarter of the entire Fraser River sockeye run -- Weaver and Nechako would have a tough time adapting to a warmer world.
"We have to recognize that every stock is different," Eliason says, waving her coffee cup in the air. "The same rules aren't going to apply to every population. How that's going to be put into practice when they're all in the river at the same time and you can't see who is who until you look at the DNA?" She shakes her head.
To avoid catastrophe -- a mystery disease, climate change, or both -- it helps to view each stock as if it contains the seeds of future diverse populations. It's comforting to know that it can take only 55 years for a salmon population to become reproductively isolated. In other words, split a population into two and within 13 generations they're on diverging genetic roads, widening their genetic heritage. That's only about two human generations.
Less comforting is knowing that this DNA-diversifying success scenario happens under the right conditions: when a population is adapting to a new salmon-friendly environment, not a rapidly changing salmon-hostile environment. To keep evolutionary pace and avoid extinction, a sockeye population needs to be big enough for individual variation too.
And that's why the salmon doctors I've met feel a sense of urgency in their inquiries. If British Columbia's sockeye populations crash quickly enough, their ability to bounce back is severely compromised -- a diverse gene pool is key to protecting themselves against new environmental challenges.
Tomorrow, the second in this two-part series: Can sockeye survive two of the more dire problems many species will face in the future: warmer temperatures and the spread of new diseases? The salmon leukemia research of DFO scientist Kristina Miller and other salmon doctors.