Researchers uncover some mysteries of arctic lampreys

Arctic lampreys are known for their toothy oral disk. Photo by Katie Shink.

If you live in Fairbanks, you may recall the excitement that spread when our flying lampreys made national news in June 2015. The lampreys had been dropped by gulls into parking lots around town.

The snake-shaped fish are abundant in interior Alaska waters. But aside from this brief moment in the headlines, little is known about how they live, eat and function as a part of the Arctic ecosystem. With limited information and funding available, University of Alaska Fairbanks researchers are trying to piece together basic information about lamprey population dynamics and diet.

Trent Sutton, a professor at the UAF School of Fisheries and Ocean Sciences, started studying Alaska’s lampreys in 2010 when nobody else was doing it. He joined forces with Andrés López, a professor at SFOS and the curator of fishes at the UA Museum of the North, and SFOS graduate student Katie Shink to study how lampreys develop and what this means for migration and feeding behavior.

Several limitations make lamprey research challenging in Alaska, López explained. First, lampreys are not a target of big commercial fisheries. Grayling, Alaska has a small commercial Arctic lamprey fishery, where about 37,000 pounds of lampreys were harvested and sold in December 2015. And lampreys are not considered charismatic. Their eel-like shape and scary, tooth-filled oral disks do not do them any favors. Finally, lampreys—along with sharks and rays—do not develop otoliths, the mineral ear bones that are broadly used in fish biology research to determine age and learn about migration patterns.

Much about the biology and life history of Alaska’s lampreys is unknown. “We don’t know how long they develop as ammocoetes (larval lampreys) in the river before some of them go out to the ocean,” Shink said. “We don’t know how long they stay in the ocean, or what causes them to return to a certain location to spawn. There are a lot of mysteries that we are working to uncover.”

This adult, marine-phase Arctic lamprey was collected in the Bering Sea. Photo by Katie Shink.

Larval lampreys are filter feeders that burrow in the mud in rivers and streams. As ammocoetes develop, they undergo a metamorphosis that can lead them to one of two life stages.

Anadromous Arctic lampreys migrate out to the Bering Sea to feed. They spend a number of years in the ocean, and then return to freshwater to spawn and die. The process is similar to the life cycle of a salmon.

Ammocoetes that develop into Alaskan brook lampreys remain in freshwater where they become non-feeding adults that spawn and die. They tend to be much smaller than Arctic lampreys.

Recent research suggests that Arctic lampreys and Alaskan brook lampreys are different forms of the same species. Scientists believe that during development, something will trigger an ammocoete to migrate or not migrate. This paired species relationship, where individuals from a single species can develop into resident or migratory adults, is seen in other lamprey species worldwide. In Alaska, this flexible strategy is found in rainbow trout and steelhead trout.

“To me personally, the big question I want to figure out is, when is that decision point when a lamprey is compelled to either migrate out to the Bering Sea or remain in its natal location and begin the spawning process,” Sutton said.

The researchers are not yet able to tackle what this trigger is, although that is the ultimate question, Sutton said. However, they are beginning to piece together information on the lamprey’s genetic history, with funding from the Alaska Department of Fish and Game, Rasmuson Fisheries Research Center and the UAF Center for Global Change Student Research Grant Competition.

Shink has been investigating whether there are genetically distinct populations of lampreys in the Chena, Gisasa and Andreafsky rivers. The Chena and Gisasa respectively feed the Tanana and Koyukuk rivers, major tributaries of the middle Yukon River. The Andreafsky is one of the final rivers to join the lower Yukon before it flows into the Bering Sea. She identified statistically distinct genetic populations of lampreys in these three locations, but the scientists do not know why the populations are unique. Shink, Sutton and López plan to do additional genetic testing on adult lamprey that were collected in the Chena River in summer 2015 to consider why this could be the case.

This fin was recovered from an Arctic lamprey's intestine, which indicates that Arctic lampreys are predators. Photo by Katie Shink.

The research team is also working to better understand lamprey feeding habits. It is commonly assumed that all species of lampreys are parasitic, meaning they attach to a host and consume their blood and maybe some flesh. Victims of a parasitic lamprey are left with a scar from the lamprey’s teeth, making them easy to detect.

However, new research uses the shapes of orals disk and other feeding structures to identify some lampreys as parasitic feeders and others as predatory. Arctic lampreys have feeding morphology that, based on this research, would indicate they are predators. This is supported by Shink’s discovery of fish bones and entire fins in the Arctic lamprey intestines. She is the first researcher to study the diets of Arctic lampreys from samples of intestinal tract contents to confirm that they are predators.

Additionally, Shink is using environmental DNA testing to identify species present in lamprey intestines. Essentially, this procedure takes a sample from the environment (in this case the contents of a lamprey’s intestines), mixes it all together, and comes up with DNA sequences that can be compared to a public database to identify species present in the sample. Her samples were collected by researchers at the National Oceanic and Atmospheric Administration during their annual Northeast Bering Sea trawl surveys.

This spinal column was found in an Arctic lamprey's intestine, which indicates that Arctic lampreys are predators. Photo by Katie Shink.

As predicted, the researchers found DNA for salmon, cod, flatfish, capelin and rainbow smelt. Unexpectedly, the researchers also detected DNA sequences for sandlance, a small, agile fish that Shink believes is much too quick to be susceptible to predation by a lamprey.

“We have a couple of theories about how the sandlance could have ended up there,” Shink said. “First, it is possible that the lampreys are scavenging sandlance during large spawning migrations. The other theory is that we’re detecting prey of prey, and that the sandlance was eaten by a cod that was later consumed by the lamprey. ”

“That’s one of the challenges of this genetic technique—determining how our results make sense, and in what context,” Shink said.

There are still many unknowns about how lampreys develop and function. The research team is eager to continue unraveling the story.

ADDITIONAL CONTACTS: Trent Sutton, tmsutton@alaska.edu, 907-474-7285; Andrés López, jalopez2@alaska.edu, 907-474-7828; Katie Shink, kshink@alaska.edu.

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