Crab Crackin’: WWU student researching how river otters might act as a natural mitigator to the invasive European green crab

WWU biology graduate student Dawson Little drives down a rutted, dirt road, and the silver pickup truck rocks back and forth as it rolls over the uneven earth. 

“This road isn’t always accessible depending on the tide and weather, but it looks good today,” Little said as tree branches scrape across the windshield. After a minute, the long curves of the Tsoo-Yess River appear. 

Little pulls onto the river’s shore and puts the truck into park. As he hops out of the car, he mentions the Makah National Fish Hatchery sits about two miles upstream, raising a variety of salmonid species. Across the river flats, Makah Bay is visible, a deep, picturesque blue. 

Ethan Gonzales, a Makah Fisheries technician and Western Washington University freshman, follows Little to the water. Little reaches into the water and grabs hold of a line. A crab trap is tied to the other end, and as Little pulls it out of the water, he finds three small, dark crabs inside.

“Oh yeah, we got green crab,” he said with a smile.

Little works for the Makah Fisheries Management’s Marine Ecology Division as a European green crab biologist. Originally from the small town of Wytheville, Virginia, located in the Blue Ridge Mountains an hour southwest of Blacksburg, Little always wanted to leave Appalachia and move west. 

“I wanted to experience as much of the West Coast as possible,” he said.

Little’s father grew up on the West Coast, and Little always felt himself drawn to the Pacific Northwest and the opportunity to work with tribal nations. In 2022, Little secured a position with the Makah Tribe and traded one coast for the other. 

“My first day in Washington was my first day on the job,” he said. 

The Makah Reservation is located on the northwestern tip of the Olympic Peninsula. About two hours west of Port Angeles, Neah Bay is the Makah Tribe’s only town, with a population of 1,550 people, 1,200 of which are tribal members. A small seaport, Neah Bay is a popular spot for recreational sport fishing, ecotourism and “van life” devotees. 

Neah Bay is also five hours from Bellingham — and that’s if you catch the first ferry. So when Little began his master’s in biology program last year, he worked with the Makah Tribe and WWU’s Biology Department to create a plan to finish his classwork in his first year. This allowed him to return to Neah Bay for the final year of his program, which will focus on research for his thesis.

Pulling crab traps is a vital part of this research. 

European green crab is an invasive species that was first reported near the mouth of the Wa'atch River in 2017, when a visitor alerted Washington Sea Grant, which in turn coordinated with Washington Department of Fish and Wildlife and the Makah Tribe. Green crabs are tenacious omnivores, eating anything they can get their claws on from native fauna like Dungeness crab to vital estuary flora like eelgrass. This, paired with their ability to survive in a wide range of temperatures, can displace and outcompete local species and destroy local habitats.

In 2021 and 2022, there was a huge spread of green crab larvae along the coast of Washington, exploding the population. Before 2021, the Makah Tribe trapped 1,000 invasive green crabs a year. Now, they average 10,000. 

“Three males,” Little tells Gonzales, who marks the data down on a sheet. The team records the size and sex of the caught crabs and counts the number of native species caught in the trap and any mortalities. Along with the green crabs, Little counts off a few Pacific Staghorn Sculpin, a slender, ray-finned fish species about 10 inches long.

“While trapping can result in limited mortality, our program is designed to remove invasive species while prioritizing the protection and recovery of native species,” Little explained. 

Little puts each crab into a plastic bag before stowing them away. When he returns to the lab, the crabs will go into a freezer to be humanely euthanized. It’s the typical fate of a European green crab captured in Washington. The invasive species is classified as “prohibited” in the state, meaning it is illegal to retain, transport or traffic live green crabs, with exceptions made for research or management under permits from the WDFW.

Green crab is of particular interest for estuary ecologists because the environmental consequences of the species are still unknown. On the East Coast, green crabs have been linked to the collapse of eel grass, a vital resource for salmon production, though Little said that may not be the whole story.

“We assume they’re these terrible, invasive species, but that’s not necessarily true. We don’t know the whole story yet,” he said. “While we know they have the potential to cause harm, they may not be throwing the ecosystem off balance like we are scared of.”

This is where Little’s true research interests lie. In particular, he’s interested in the apex predator of the estuarine ecosystem: the river otter.

Once the crabs are noted and collected, Little heads further down the river’s shore. After climbing underneath tangled tree roots, he points out a few tracks in the sand. 

“These are river otter tracks,” he said. “You can identify them by the slightly enlarged tip of their fingers and prominent back pads on their paws.” 

The tracks surround an otter latrine, a small mound of earth near the water’s edge. 

“Otters use latrines as a form of communication with each other,” Little explained. “North American River Otters are one of the most social otter species in the world.”

Otters communicate through their scent and scat, and they often use latrines as a hub for social connection. It is not uncommon for otters to play with each other at latrines. This latrine even features a slide.

It’s the otter scat Little is most interested in. After spotting some on the beach, Little squats down and pulls on a pair of nitrile gloves. 

“We try to keep things as sterile as possible,” he said as he scoops the piece of scat into a container. Specimens are sealed immediately in the field, then brought back to the lab where they are stored in a freezer. 

Scatology and ‘Poothenol’

Little collected otter scat for two years before he enrolled at Western to prepare for this project. By studying what the otters eat, Little hopes to answer whether green crab are being integrated into the natural ecosystem, showing that they are not only predating but also being preyed upon.

“If there’s one thing we know about river otters it’s that they’re highly opportunistic feeders, willing to eat almost anything they can catch or find,” Little said. 

Estuarine river otters are unique because of the amount of crab and hard-shelled prey they eat. This leaves behind hard pieces of shell in their scat, which means it’s easier to tell if the otters have been munching on green crab. 

However, the hard remains do not tell the full story. Otters also eat a number of soft prey which can only be identified through molecular analysis. Little is planning to combine the two processes to hopefully connect both pieces of information on the river otter’s diet, a technique that is still considered relatively novel.

This process is called molecular scatology.

“It is the study of genetics through poop,” Little explained.

After clearing away the cardboard boxes still sitting in the center of his lab, Little loads his samples into a refrigerator where they’ll wait until the beginning of fall and the end of sampling season. As evidenced by the cardboard boxes, Little’s molecular biology lab is brand new. 

It’s not a large room — no more than five people could stand inside, and that would be a squeeze — but it’s filled with everything Little will need for his research. He has a few more pieces in the mail to complete the lab, but his favorite instrument has already arrived: an expensive, delicate and extremely precise scale, the kind that a data-driven scientist loves. He also points out a retro fume hood created by a former Makah Fisheries employee that Little unearthed from storage. 

“It even works,” he said, powering it on to demonstrate.

While this is the homebase for Little’s research, the lab will meet several needs for the tribe by allowing fisheries employees to study sea lions, seals, salmon and even oil spills. By having an in-house lab, the Makah will be able to save money they previously spent on outsourcing work to external labs, which in turn allows them to dedicate more resources toward ecological preservation.

Little’s process to study the scat is straightforward. First, Little places the scat sample into a mesh bag then dips it into ethanol like a teabag to create a slurry — or, as Little coins it, “poothenol.” Once all of the scat has been dissolved into the slurry mixture, Little examines the remaining hard bits by hand.

Then, Little analyzes the poothenol on a molecular level to capture any other prey that the otter may have consumed. The combination of these two methods offers a more complete picture of what river otters are eating and will provide a more accurate percentage of how much of their diet is green crab.

‘A Whole Story of Western Folks’

Little is not the first person to study river otter predation on green crab. In 2019, then-WWU biology graduate student Bobbie Buzzell conducted a similar study using river otter scat data collected from the Wa’atch and Tsoo-Yess rivers.

Like Little, Buzzell collected samples from the field in the spring and summer of 2019 and used additional samples collected by the Makah Fisheries in 2018 to determine the river otter’s diet. Buzzell handled identification of crab parts and partnered with National Oceanic and Atmospheric Administration scientist William Walker to identify any fish species.

“The final conclusion was that yes, river otters did happen to eat a few green crabs, but it was extremely insignificant,” Buzzell said, who now works as the natural resources grant manager for the Lummi Tribe.

However, the other significant result of Buzzell’s study was a more comprehensive picture of the river otter’s diet, she said, which would allow future researchers a better understanding of how river otters fit into estuary ecosystems.

After Neah Bay’s green crab population boomed in 2022 and therefore made green crab a more easily accessible food for river otters, Little and the Makah Tribe felt as if there was an opportunity to re-examine if green crab had become a significant prey source.

Both Little and Buzzell worked under the guidance of Professor of Biology Alejandro Acevedo-Gutiérrez in his Marine Mammal Ecology Lab, who has been partnering with the Makah for over 10 years. Little is also advised by Professor of Biology Dietmar Schwartz, who advises Little on the molecular analysis portion of his research and with whom Acevedo-Gutiérrez has collaborated for a dozen years.

The connections between Western’s Marine Mammal Ecology Lab and the Makah Tribe are bountiful. Adrianne Akmaijian, the Makah’s marine ecologist and where Western’s connection to the Makah began, earned her master’s degree in 2016 under Acevedo-Gutiérrez’s advisement. She also worked with Buzzell on the initial river otter study and currently supervises Little. 

Acevedo-Gutiérrez’s former student Erin D’Agnese collaborates frequently with the Makah Tribe and Little with her company Wild EcoHealth. Current WWU senior Ellie Taylor partners with Little to use genetic markers to identify the sex of a river otter by its scat — an important piece to the puzzle of understanding river otter behavior and how prey patterns may differ between sex. Even Little’s own roommate and fellow Makah employee Jasper McCutcheon studied within Acevedo-Gutiérrez’s lab as an undergraduate.

“It’s a whole story of Western folks,” Little said. 

The lab’s ongoing partnership with the Makah and culture of collaborative research is a marker of the excellence of both its students and the research they perform, Acevedo-Gutiérrez said. 

“One of the things we pride ourselves on is that we collaborate with a lot of people, including former students, and that we have such a strong network of connections,” he said.

Current and former student research in Acevedo-Gutiérrez’s and Schwarz’s labs continuously inform Little’s current research. For example, the process to identify genetic markers Taylor uses to distinguish river otter sex was adapted from research a former Marine Mammal Ecology Lab student developed on harbor seals. 

“It’s almost like a whole spiderweb network of former students and collaborators that inform the research,” Schwarz said.

“Know your ‘green crab’ from your ‘green’ crab”

After leaving the Tsoo-Yess River, Little drives to the site where the first European green crab in Neah Bay was discovered. The Wa’atch River runs alongside a small neighborhood a short drive down the road from the Fisheries office. 

Gray clouds loom overhead as Little wades through the shallows toward another trap. Unlike so many rivers in Washington that are fed by glacier melt, the Wa’atch River is completely rain-fed. 

Little pulls the trap’s line and hauls in a collection of greenish crabs, some of which are significantly smaller than the ones caught earlier. 

“This is a hairy shore crab,” Little said as he takes one of the smaller crabs into his hand. “They are often mistaken for European green crab because of their color.”

Their name can be misleading. 

“Green crabs are not always green,” Little explained. When a young European green crab molts, it can change its shell color to match its surroundings, and adult crabs often have yellow markings or orange joints. 

“You have to know your ‘green crab’ from your ‘green’ crab,” Little said. 

The best way to correctly identify a European green crab is by the five spines on each side of the shell. If people think they have discovered a European green crab, they should report the sighting to the WDFW and, more importantly, leave the crab alive. This mitigates the risk of well-meaning citizens accidentally disrupting a native crab species.

Little has noticed a decrease in the number of green crabs that he captures each day, which he hopes is due to the Makah’s trapping and mitigation efforts. The previous week, Little led a trapping blitz where the Tribe invited colleagues from other agencies, including Washington Sea Grant and WDFW, and volunteers to place traps along the rivers for a week. The traps are checked every 24 hours, and after three full days of trapping, the team caught more than 2,000 crabs, which would be processed within the week. 

In addition to the trapping blitz, the Makah has volunteers in the field each week during the trapping season, which runs from April to the end of September. During peak season, Little estimates there’s at least one green crab caught per trap placed. 

Despite this, Little doesn’t see an end to the green crab invasion any time soon. 

“We could trap every crab in Washington, and it wouldn’t matter because they’d come from California, B.C. or Oregon,” Little said. “Invasive species do not see borders.”

This is why uniform laws are important, Little said. Unlike Washington, green crab is not a prohibited species in California and Oregon, and some places along the West Coast even allow for the sale of green crab. 

It’s another reason why Little hopes the river otters will prove to be a natural control to the green crab population. It would be redemption for a species that was once considered a nuisance themselves, Little said. 

In the 1800’s, river otters were largely eradicated from the U.S. due to over-trapping. Restoration efforts were made to recover the population, and the river otter’s resurgence is seen as a success story. Unfortunately, river otters are now often seen as pests, especially because they eat a lot of young salmonids and can pose issues for hatcheries. Little hopes by showing river otters may help control the green crab population, their perception will change. 

“This may provide a motive for people to not just kill them or to relocate them,” Little said. “Or it will just show people they do play an important role in our estuary ecosystem.”

Little will spend the next year working through his backlog of scat samples to test if his theory is correct. Little plans to remain working for the Makah after his thesis is completed and is looking forward to applying his findings and contributing to the Neah Bay ecosystem and the Makah people however he can. 

“To feel like I have some sort of impact and to be able to give back is really nice,” he said.

To learn more about Little’s research or the work being done in Acevedo-Gutiérrez's lab, visit https://faculty.aceveda.wwu.edu/ and to learn more about the Schwarz’s research, visit https://www.researchgate.net/profile/Dietmar-Schwarz

Interested in starting your own research journey? Visit https://gradschool.wwu.edu/ to learn more about learning at Western.

Mikayla King (‘17) covers the College of Science and Engineering and Woodring College of Education for the Office of University Communications. Reach out to her with story ideas at kingm24@wwu.edu.