State regulators have enacted emergency harvesting closures in Brunswick and Harpswell following a softshell clam die-off linked to an ongoing harmful algal bloom.
The Department of Marine Resources halted picking shellfish in Maquoit Bay and part of Middle Bay last week after local shellfish committees reported mounting harm to clams in the area.
In Brunswick, town officials reported that 80% of adult clams were stressed, dying or already dead, according to the department.
Brunswick Coastal Resource Manager Dan Devereaux said the aim of the closure is to protect remaining juvenile clams from additional disturbance.
“There’s not a lot of harvestable product out there anymore, and the ones that do survive, we’d prefer they stay in place and provide seed for the following years,” Devereaux said.
Brunswick was the biggest softshell clam port in Maine in 2025, where harvesters pulled in almost $1.8 million worth of clams, according to the Department of Marine Resources.
The Department of Marine Resources started tracking a spreading bloom of Karenia mikimotoi, a type of phytoplankton in early September. The bloom has since spread across the Maine coast but has been especially concentrated in Casco Bay.
Nick Record, a senior scientist at the Bigelow Laboratory for Ocean Science, said the first Karenia mikimotoi bloom was recorded in the Gulf of Maine in 2017.
The algae is not toxic to humans, but it can deplete oxygen in the water and choke out other marine organisms, Record added.
“As they break down and decompose, that decomposition also uses up a lot of oxygen. So, a lot of time when you see fish mortality it is just due to those really low oxygen levels,” Record said.
At least four harmful algal species that are new to the Gulf of Maine have been identified in the last decade, according to Record.
He expects climate change, shifting currents and stowaways on container ships will move more species into the Gulf of Maine.
“I would expect us to see more new things as time goes on and some of those things might be harmful,” Record said.
This story appears through a media partnership with Maine Public.