Cape Cod Bay Oxygen Levels 'Concerning.' What It Means For Lobstermen

CAPE COD, MA — The waters in the southern part of the Cape Cod Bay are showing signs of low oxygen levels, a signifier that, if things get worse, could mean bad, bad things for lobster fishermen.

A Sept. 15 message from the Massachusetts Divison of Marine Fisheries reported that dissolved oxygen levels are decreasing in some southern parts of the Cape Cod Bay known to researchers as "The Blob". This phenomenon, called hypoxia, can cause major issues for wildlife, as the bottom waters in an area experiencing it don't have enough oxygen to sustain life for species like lobsters, crabs and finfish.

Thus far, measurements collected by the DMF, Center for Coastal Studies and commercial lobster fishers have measured levels nearing less than 4 milligrams per liter, a figure which is considered "mildly hypoxic." Less than 2 milligrams per liter is considered "severely hypoxic."

According to the report, no prolonged periods of severely hypoxic oxygen levels have been reported this summer, but the current trend is "concerning." Officials are now asking lobster fishermen to not only be aware of what they're catching, but to also consider moving their operation elsewhere.

"Many mobile bottom dwelling animals like lobsters will move to avoid hypoxic conditions when they can, but will die if stuck in traps and exposed to hypoxia for more than a few hours," officials said.

"DMF urges those lobster fishermen working in or near the area to be on the lookout for signs of hypoxia, which includes unusual amounts of lethargic or dead lobsters, crabs, or finfish in the traps. DMF recommends fishermen check traps frequently, and possibly consider moving gear out of the affected region to prevent trapping lobsters or crabs in hypoxic conditions."

The Blob

Though severely hypoxic water has yet to be reported this summer, it has happened before, and in this same area of the bay.

Lobster fishermen in September 2019 pulled up hundreds of pounds of dead lobster due to what the DMF now calls a "severe hypoxia event."

The Cape Cod Bay Study Fleet was established in the days after, which allows the DMF to continue to monitor the waters for hypoxic conditions.

Read more about The Blob here.