Along Maine’s coast, students are contributing to the science of invasive species by collecting and counting crabs. Their startling observations are allowing young Mainers to observe the changes on the coast where they live in real time — and now they’re planning to take action.
For the past few years, the Gulf of Maine Research Institute has spearheaded a citizen science project where students identify and catalogue two invasive crab species — the European green crab and the Asian shore crab — along with native crabs. Recently, students from Kennebunk High School counted the most crabs that the institute has ever seen in one area.
The record-setting numbers are indicative of an exploding invasive crab population, which wreaks havoc on Maine’s fisheries and coastal ecosystems by eating their way through local shellfish and outcompeting native species. By enlisting local students to help count the populations, scientists are collecting more data and also inspiring the next generation of environmental activists.
In early October, the students from Kennebunk High School recorded 56 European green crabs in one plot, and 41 European green and 20 Asian shore crabs in another.
They did not find a single native crab in their collection that day.
Marissa McMahan said that she is alarmed, but not surprised by the findings. Warming temperatures may be speeding up the development rate of the crabs, causing them to reproduce more quickly, the director of fisheries at the Massachusetts-based coast ecology research non-profit Manomet said.
“We do green crab surveys through midcoast Maine and we’ve seen higher density than we’re ever seen before, up to four to five times as much magnitude,” McMahan said. “This year seems to be a record-breaking year for green crabs up and down the coast.”
The institute’s intertidal crab citizen science project started in 2018 when McMahan realized that scientists were missing a lot of important data about invasive crabs.
“We began developing a program at Manomet to look at creating fisheries and markets for the invasive European green crab,” McMahan said. “As part of that work we started looking around for information on green crab populations and realized there wasn’t a whole lot out there.”
McMahan had worked at the Gulf of Maine Research Institute as a graduate student and stayed in touch with its education department. Together, they developed an idea: let Maine students count the crabs. As the kids collect data over the years, scientists will have a better understanding of the invasive populations.
“In the past, our understanding of the green crab population has been based on very short windows in time,” McMahan said. “We don’t have a good understanding of the populations over time. That’s one of the good things that this data provides.”
The Gulf of Maine Research Institute and Manomet developed a crab collection protocol for students, which included identification, sexing and a “squeeze” test to determine whether crabs are molting. Teachers can sign up and go through training with the institute, and then scientists validate the data.
The project is a good fit for the institute’s citizen science initiatives because the students collect meaningful data that scientists can actually use, but it doesn’t require specialized or expensive equipment, according to Meggie Harvey, science curriculum specialist at the Gulf of Maine Research Institute.
Plus, European green and Asian shore crabs are fairly easy to tell apart — the former has five distinct spines around its eyes, while the latter has a unique banding pattern on its legs — and are distinct from many of the native species that the students might come across.
Since it started, the project has amassed 33 different schools to collect crabs, including Kennebunk High School, which conducted their first crab collection this year.
Ella Boxall and Lily Martin are seniors at Kennebunk High School in a class taught by Melissa Luetje called Gulf of Maine Field Studies. Luetje worked with the Gulf of Maine Research Institute to develop a field trip with her students in early October where they went out to nearby Redin Island to collect data on the crabs found in their plot, also called “quadrats.”
That’s where they counted the record number of the invasive critters.
“It was a little bit disappointing how many of them were there,” Boxall said. “That was the biggest challenge for me was to see how many there were found and knowing how big of a challenge there will be to get [them] out of our ecosystem.”
The students could also connect the dots with what they were seeing in their own communities.
“We learned in class that one green crab can eat 50 clams a day,” Martin said. “No wonder you can’t get clams at seafood restaurants.”
McMahan said that over time, the data will be useful to help municipalities planning when to seed their clam flats ( softshell clams are a particular delicacy for invasive crabs), and for researchers working to find markets for invasive crabs.
“We’re starting to see students and school groups being able to do this throughout multiple school years,” McMahan said. “It’s really useful on our end as research and for management purposes.”
The students who collected this data were not only able to flag the bumper population for researchers, but the experience also inspired them to do more when it comes to the invasive crab populations. Boxall and Martin are part of their school’s Environmental Action Club, and they hope to use what they learned in class to lead a community project about invasive crabs.
Because of the useful data it has provided and the inspiration it has instilled in participants, Harvey said that the Gulf of Maine Research Institute plans to run this citizen science project “indefinitely,” and she hopes that the project will continue to grow, expanding to schools even further east to get a more complete picture.
“At this point we have more questions than answers about what it is that we’re seeing and what the implications are,” Harvey said. “It is really exciting to have the student community and broader community engaged in these questions.”