I remember vivid visuals which manage to compress something immense into the space of seconds: the cosmic force of a big bang flinging matter across the universe, Ice Age glaciers clamoring down from the north then retreating again, time-lapse footage of the tides’ rhythmic breathing. Even commuters dancing the stop-and-go of a traffic light.
An Arctic grayling (Thymallus arcticus) is a fish; it’s also a commuter of sorts. Its entire life is a rhythm of motion undertaken to survive and thrive.
Motion and timing
Radio telemetry data gained from tiny radio transmitters implanted in the grayling of Alaska’s upper Kuparuk River tell the tale: fish disperse from the winter haven of Green Cabin Lake to find gravelly stream beds where they spawn. Then old and young alike traverse the waterways seeking food; like bears, they need to fatten up to survive the winter months. Before winter’s jaws snap closed and the bulk of Alaska’s waterways freeze solid, the population has to hightail it back to the fairly deep fairly safe waters of Green Cabin Lake. Next year when the Kuparuk River thaws the pattern will begin again.
Jeff Adams, fishery biologist with the U.S. Fish and Wildlife Service in Fairbanks, Alaska, values the population movement and timing data gained from grayling radio telemetry. Even though there are likely other groups of Arctic grayling which live far downstream near the Arctic coast, it appears that the upper fish rarely intermingle with the lower river groups.
“From a management perspective, that’s good to know. If there is ever a high harvest pressure on the fish, say, off the Dalton Highway, then we know that the fish that they are catching off the Dalton are likely fish from the upper river and management actions could be taken to conserve these upper river fish.” ~ Jeff Adams
Productive ecosystems, biodiversity
Fishing? Oh yes. Besides providing meals for Alaska’s animal kingdom predators, the grayling also fills human dinner plates.
“They are a very, very popular species for rod and reel sport anglers. As well as the smaller communities; they are very important seasonally for subsistence fishing. They are one of the first species that folks capture, to have fresh fish after a winter of eating dried and grocery store food.” ~ Jeff Adams
Heidi Golden, Ph.D. candidate at the University of Connecticut (Storrs Campus), doesn’t love eating grayling, probably because of her work studying the fish – she’s come to appreciate the species.
“They are the only fish species in a lot of these tundra streams likely because of the harshness of the environment. There are not many species that can actually travel into those rivers and not freeze solid and die. Grayling are amazing creatures.” … “And, they help sustain a more diverse and productive ecosystem.” ~ Heidi Golden
Golden outlines an intricate connection between the roughly 5,000 grayling who overwinter at Green Cabin Lake and the healthy trout population that call the lake home year-round. The grayling travel downstream, feeding and gaining weight, until they have to retreat to Green Cabin Lake to survive the long winter. They’re transporting nutrients to the lake, both because the trout flat-out eat them and because grayling poop provides a vital meal to algae and phytoplankton, which feed zooplankton, which feed fish, which feed everything from wolverines to eagles. In the Arctic, where lack of nutrients is often one of the limiting factors to life, they’re actively making the local food chain more robust.
Golden’s work requires long treks along Alaska’s waterways. She’s capturing young fish and taking fin clips, then using those tissue samples to analyze genetic distribution. She has to be careful to sample from different groups to avoid accidentally catching siblings traveling near one another. This genetic map will help delineate how individuals from different grayling populations are moving across the landscape. Golden also collaborates with Dr. Linda Deegan from the Marine Biological Laboratory (Woods Hole, MA) by injecting fish with a passive integrative responder tag (PIT tag), a tiny coated wire bearing an identifying code, just like the ones people can have implanted in a pet dog. Unlike a radio transponder tag the PIT tag doesn’t carry a battery. Instead, antenna arrays set up along the river (arrays including a wire loop extended into the water) detect and record when a tagged fish passes by, where, and which specific individual it was.
Resilience or vulnerability
Why all this effort to understand the motions of grayling populations? It’s because these fish, which already live in an extreme environment, are currently facing extreme environmental changes.
“I study Arctic grayling on the North Slope of the Brooks mountain range because this is an area which is experiencing hydrologic changes due to climate change. Those changes hold potential to increase aquatic habitat fragmentation. And where there is habitat fragmentation you often get isolation of populations, which could then lead to population decline. So studying the grayling where climate change is happening very rapidly can give us a handle on issues about habitat fragmentation and population resistance to climate change and resilience to climate change.” ~ Heidi Golden
“The critical piece for them is to be able to get back to Green Cabin Lake in early fall to overwinter. Understanding the effects of habitat fragmentation due to drought and climate change – those are critical pieces, no doubt about it.” ~ Jeff Adams
Golden and Adams are using grayling as an ‘indicator species.’ Impacts from climate change are being noted throughout the world, but because of a trend termed Arctic amplification the Arctic is experiencing more dramatic changes – for example, Arctic temperatures are increasing twice as swiftly as mid-latitude temperatures. If these scientists explore and document what happens as grayling populations grapple with fast-changing habitats, their results can both inform grayling management strategies and guide future management of other species which similarly rely on multiple habitats.
“All of a sudden the aquatic landscape is changing. How will this landscape-level change affect the fish populations living within this aquatic network?” … “The lessons we learn from Arctic grayling can then be transmitted to other species that haven’t experienced the impacts of climate change yet but probably will in the future.” ~ Heidi Golden
Frontier Scientists: presenting scientific discovery in the Arctic and beyond
- Interview with Heidi Golden, Ph.D. candidate at the University of Connecticut, July 2014
- Interview with Jeff Adams, fishery biologist, U.S. Fish and Wildlife Service, July 2014