The program involves a number of partners, including the Bristol Bay Native Association (BBNA), a consortium of 31 tribes whose mission includes providing educational opportunities to the native people of the Bristol Bay region. Each summer, BBNA research interns contribute to the Alaska Salmon Program, and this year Nadezdha Wolcott (below left) and Malcolm Upton assisted with hair sample collection as part of the noninvasive genetic component of the research.
“The bears were really active this year, the fourth of our study,” says Professor Wirsing, who recently returned from a field trip to Alaska. “So we really appreciated the interns’ help in collecting all of the hairs snagged on our barbed wires!”
Every year,hundreds of millions of salmon swim from the Pacific Ocean into streams and rivers up and down the West Coast from California to Alaska. They make their way, with remarkable precision and determination, to spawn in the very grounds where they were born. “It’s one of, if not the grandest migrations in the whole world,” says Professor Aaron Wirsing, who recently returned from two weeks at the Fisheries Research Institute in the village of Aleknagik, Alaska.
This summer, the total number of salmon in Hansen Creek is already double previous counts.
This field season, while the researchers haven’t seen as many bears, they are witnessing a record salmon run that continues to pour into the system. The latest count for just one of the streams, Hansen Creek, is already more than 50,000 salmon—which is more than double the previous record for the whole summer. Picture those fish, some 20,000 at a time, packed into a two-kilometer stretch of water only four meters wide and barely five centimeters deep. That’s a lot of fins in the water, and it makes for an unforgettable sight. “It’s like salmon soup,” says Professor Wirsing.
Before the salmon embark on that last leg to the spawning ground, they often pool at the entry point to the creek and wait days, even weeks, before venturing into the current. Why they pause at the creek mouth, and what triggers the last desperate dash, isn’t entirely clear, though it’s thought to be partly a response to predation risk, with the salmon entering in huge waves to overwhelm their predators—in this case, brown bears. The presence of fish in the creek, with silt kicked up by spawning salmon upstream, might also be a cue for others to follow.
In the best of years, salmon causalities are still fairly high as they near the end of this journey (and all Pacific salmon perish after spawning). Some lack the energy to make the final surge up the stream, or they get stranded in the shallows, sometimes just feet from their destination; others get snapped up by bears, or they provide a gruesome feast for birds that peck away at the half-exposed fish. This year, as well, the salmon are facing extreme low water levels. In many spots, the sockeye barely have a few centimeters to buoy them up the stream, and they have to muster an even more heroic effort to splash their way to the finish.
In many places, the salmon have to make their way through only a few centimeters of water.
It’s too early to know precisely what has fueled this record salmon run, says Wirsing, but it could be linked to favorable oceanic conditions (e.g. lots of food at sea). One clear consequence of the high numbers, though, is higher pre-spawning mortality, due both to stranding and to low dissolved oxygen levels in the crowded streams. These salmon will also bring a huge pulse of marine-derived nutrients, which will bolster freshwater invertebrate and bear populations, and even make their way into riparian plants. One other longer-term effect, too, is that there should be another large run in four years when the offspring of these salmon have matured—provided, of course, that enough fish this year are able to spawn and oceanic conditions are again favorable.
Words and photos can’t fully capture the intensity of the annual run, but luckily Professor Wirsing got some great video (below) of the salmon scrum at the entrance to Hansen Creek. It’s like marathoners jockeying for position before the start of a race!
But for all the iconic footage of salmon runs, this annual rite of passage and predation has gone largely unstudied from the point of view of individual bears—especially outside of easily observable areas.
The challenge is that observations of bears are generally too few and too close to reveal natural feeding behavior, so most of what we know about the bear-salmon relationship comes from fish carcass surveys: We see what’s been eaten, but not always who did the eating, or how often or where or when. That leaves a lot of unknowns, including how many bears hunt along salmon spawning-streams, and whether bears return to the same stream year after year.
To answer these questions and others, two units in the College of the Environment—the School of Aquatic and Fishery Sciences (SAFS) and the School of Environmental and Forest Sciences (SEFS)—have launched a coordinated research project.
Professors Aaron Wirsing, left, and Tom Quinn. Since 1993, Quinn’s research has explored a number of dimensions of the salmon-bear relationship, including the effects of stream characteristics on bear predation rate, size selectivity, density dependence, evolutionary consequences and links to nutrient cycling.
Led by SAFS Professor Tom Quinn and SEFS Professor Aaron Wirsing, this new study is investigating coastal brown bear (Ursus arctos) abundance and behavior along sockeye salmon (Oncorhynchus nerka) spawning streams in Bristol Bay, Alaska. Their project draws from decades of existing salmon research and introduces a completely new perspective by exploring individual brown bear behavior, including monitoring bears through remote cameras and collecting hair samples for DNA analysis.
The research team is housed at the Fisheries Research Institute, a program within SAFS, and based in the village of Aleknagik. In addition to Professors Quinn and Wirsing, the crew includes SAFS graduate student Curry Cunningham and Professor Lisette Waits from the University of Idaho.
Their work began in 2010 by placing the first cameras along salmon-spawning streams in the Wood River Lakes System. In July 2012, they then deployed barbed wire across three streams to begin snagging tufts of hair from foraging bears. This past summer, they expanded the research area and deployed two barbed wires each on six streams. One wire per stream is paired with a remote camera trap to document what happens when bears encounter the wires. The wires are set just high enough—55-60 centimeters—for bears to step gingerly over them, often leaving small tufts of hair behind (when good samples are collected, they call it a “good hair day”). The hairs, in turn, yield DNA samples that help researchers identify individual bears.
A tuft of brown bear hair snagged on a wire.
The study is designed to be noninvasive, so among the questions to answer was whether the wires would impact or otherwise disrupt bear behavior and hunting. Judging from the camera images so far—including many taken at night (see slideshow below)—the bears appear largely unconcerned with the wires, often stepping over and under multiple times in a single encounter (in the process, of course, leaving collectible tufts of hair).
In the first year of hair sampling last summer, the team collected 74 tufts from wires along Bear, Happy, and Hansen creeks. They have analyzed 41 of the samples so far and have successfully identified 15 different individuals—eleven females, four males, and all brown bears.
Field work is just winding down for this summer (at left, check out a slideshow of photos Professor Wirsing took a few weeks ago). They plan to continue the project for a few more years, and as researchers sort through several hundred new samples to analyze, they’re excited to open this window into a largely unseen and unstudied realm of bear behavior.
“Outside of a few highly visible areas, such as the McNeil River, the behavior of brown bears foraging on salmon has been largely shrouded in mystery,” says Wirsing. “We hope our work will reveal how feeding and social behavior of individual bears are shaped by the arrival of migrating salmon—and by extension how coastal brown bear populations might be affected by changes to the size and timing of salmon runs.”
*** Super Salmon In the short video clip below, Professor Wirsing captures sockeye salmon swimming up Hansen Creek, which in some places is only a couple inches deep as it approaches Lake Aleknagik. You’ll get a glimpse—a tiny glimpse, mind you—of the herculean effort it takes for salmon to reach their spawning grounds. Their exertion is nothing short of heroic during this brutal slog. After all, even when they manage to dodge the maw of a hungry grizzly, they still have to muscle their way through narrow, shallow streams to reach their final destinations. In some cases, a few of the larger males get too fatigued to maneuver through the shallowest sections and end up stranded. Those beached souls then sometimes have to suffer through gulls pecking their eyes out as a final insult. No question, it’s an unforgiving business.