Wild American oysters, long considered extinct in Midcoast Maine, have returned to the region, according to a recent study.

With the help of local shellfish harvesters, researchers from the University of Maine identified the oysters in nearly 40 areas along the coastal Damariscotta River. And they raised questions about whether aquaculture farms could be responsible for the species’ return to the wild.

The study also reported steep declines in soft-shell clam and mussel populations.

However, the findings were just a part of the overall goal: to improve stewardship of estuaries and their shellfish populations.

Co-authors Sarah Risley, a marine science Ph.D. candidate, and Heather Leslie, a marine conservation scientist and professor, said they were looking for empirical proof of the effectiveness of using knowledge from fishermen to inform research and data.

The study is a part of a growing effort marine scientists and officials are making to invite fishermen to the table. The ultimate conclusion, the study asserts, is that industry input and participation helps scientists and rulemakers better understand Maine’s marine ecosystems — and, in turn, can help them improve the regulations they write that affect fishermen’s day-to-day lives.

“As researchers, we can only be out in the field for a couple months out of the year. We talked to harvesters who spend 365 days a year on the mud flats, sometimes two tides a day,” Risley said. “Ultimately, they are the experts on the ecosystem.”

THE NEED

The town of Damariscotta makes decisions about how to steward, sustain and enhance the local shellfish resources — like how many commercial shellfish licenses to allocate and what areas to close off to fishing.

The town and its Shellfish Committee had anecdotally heard from harvesters that there were visible changes in shellfish populations in estuaries of the Damariscotta and Medomak rivers.

But the town has struggled to make those decisions. Leslie said there haven’t been regular biological surveys to understand the populations. And scientists have struggled to conduct this research.

“It’s hard for us to navigate through the mud, work with the tides and collect shellfish to gather data in consistent ways that can be used for management,” Leslie said.

Using the people who navigate these flats day in and day out, and whose families have dug their catch there for generations, is an obvious solution, Leslie and Risley said.

THE FINDINGS

The study kicked off in 2020 and ran until 2021. Due to complications during the start of the coronavirus pandemic, researchers gathered information from local experts, instead of gathering the shellfish themselves. The local experts included harvesters, oyster farmers, conservationists and harbormasters.

The groups worked together to build a map of the regions within the two estuaries and then spoke in formal interviews to share their experiences, provide context and posit theories on what is causing these changes.

The researchers intentionally did not go to validate the locals’ findings with their own work.

“Despite recent progress in collaborative research, local knowledge is often treated as something of lesser value than knowledge generated or curated by professional researchers,” the study states. “Local knowledge is often treated as just another form of data, subject to the structures and power hierarchies. … Researchers should be careful to not concentrate power away from local knowledge holders and resource users.”

The fishermen reported a low amount or absence of soft-shell clams all along the Damariscotta River and medium- to low-populations in the Medomak River estuary.

There’s also the resurgence of the wild oyster. The species was once abundant, but populations fell because of rising sea levels, changing tides, overdevelopment, overfishing and pollution. The oyster has long been considered “functionally extinct” in Damariscotta and very rare in Maine at large, according to the study.

Not much on those fronts has changed to encourage the return of the wild oyster. But the growth of aquaculture has.

FUTURE RESEARCH

Today, there are around 60 oyster farming sites along the Damariscotta River, according to a list of aquaculture leases from the Maine Department of Marine Resources.  The locations where fishermen reported oyster populations are concentrated around those sites.

Fishermen believe that oyster larvae are spreading into the water from those farms.

But they don’t necessarily feel excited about the potential for a new catch. Many believe that wild oysters are taking down the soft-shell clam population.

“We are wild clammers, and we want to stay that way,” one fisherman told researchers, according to the study.

The study doesn’t conclude that the fishermen’s theories of the “why’s” are accurate. But scientists and Damariscotta officials are now launching research projects to explore the fishermen’s ideas.

“This has emphasized the valuable depth and the multigenerational quality of the knowledge and information that harvesters have,” Risley said.

And they hope that federal scientists and regulators take note.