Blue crab watch · Callinectes sapidus

Blue crabs have reached the Gulf of Maine

Blue crabs were rare north of Cape Cod. Since about 2019, people have found them in harbors, flats and lobster traps from Massachusetts to Down East Maine. Press play to watch the sightings add up.

Report a blue crab sighting
…Sightings
—Farthest north, US coast
0Crabs counted in survey reports
Cape Cod, Rhode Island, Connecticut
20132016201920222026

When they turn up

Share of each source's sightings by month. Bars point outward from the center; the shaded arc is July–October.

Survey reports have dropped

All Manomet survey reports per year. Fewer reports means fewer people reporting, not fewer crabs. iNaturalist sightings in the Gulf of Maine held steady over the same years.

Seen a blue crab this year? Report it.

Every report helps, even a single crab, a dead one on the beach, or just a claw. Note where and when you found it, and snap a photo if you can. Your sighting goes straight into Manomet's survey and helps show how far north blue crabs are spreading.

Report a blue crab sighting
The crab

What's a blue crab?

A swimming crab with paddle-shaped back legs and bright blue claws. Females have red tips on their claws. Adults are 5 to 9 inches across the shell. Common from Cape Cod south to the Gulf of Mexico, they were only an occasional visitor in the Gulf of Maine.

The change

Why it matters

The Gulf of Maine is warming faster than most of the world's ocean. Warmer winters may let more blue crabs survive here. They eat clams, mussels and other crabs, so researchers want to know where they show up, how many there are, and whether they're breeding.

You can help

How to help

If you catch or find a blue crab in Maine, New Hampshire or northern Massachusetts, report it, even if it's dead or just a claw. Note where and when, how many, and take a photo with something for scale. Each report helps track how far north they've spread.

Report a blue crab sighting