Invasive SpeciesGreen crab

Carcinus maenas
FOUND by Blue Crabs
Cape Elizabeth
ID Confirmed
Quality checked by Mrs. Young
Peer reviewed by Cape Roses
Field Notes
October 24 2017. We are collecting data on Green Crabs. We are investigating at Kettle Cove Beach, in Cape Elizabeth, to find out if there are Green Crabs there, and if so, how many. We arrived at around 9:20 AM, greeted by a strong cold burst of wind and the smell of seaweed. The sea air is cold and crisp (About 63ºF) and whips us in the face as we jog towards the tide pools, ready to begin our search. The area we found our crab in was rocky with lots of seaweed. At first, it was difficult to find and catch a crab due to its speed, ability to hide, and the large amount of other students looking for them. We found our crab within the first 5 minutes, which was surprising because it usually takes a lot more time and effort. Most of the crabs we found were hiding underneath rocks. It was very difficult holding crabs still for photos, because it was small and quick, and the wind was very strong. The cloud cover percentage is about 95%, and there is no precipitation. It was ebbtide,(when the tide is going out to the ocean) with lowtide at 8:33 AM and high tide at 2:39 PM.
A sketch of our study site.
Supporting Evidence
Photo of my evidence.
This is a Green Crab. Green crabs have pentagon shaped shells, which is the shape of the specimen that we found (which we show in our photo). A way to remember this is that a pentagon has 5 sides, and “Green” has 5 letters. This is not an Asian Shore Crab because Asian Shore Crabs have a square-like shape, not a pentagon.
Photo of my evidence.
This is a Green Crab. Green Crabs have 5 spines on the side of each eye, as it shows in this photo of our specimen. This is not an Asian Shore Crab because they have three spines, not five.
Photo of my evidence.
Another reason why this is a Green Crab is Green Crabs have two thin, pointy claws. The crab we found that is shown in the photo also has two thin, pointy claws. In this photo, you can see the thin claws, one closed, and one open. This is not an Asian Shore Crab because they have fleshy bulb-like structures in their claws, Green Crabs do not.
Species Observation: Species Looked For
Did you find it?: 
I think I found it
Scientific name:
Carcinus maenas
Common name:
Green crab
Sampling method: 
Just looking around
Photo of our sampling method.
Place Studied
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Map this species
N 43.561421 °
W -70.218608 °
Observation Site Information
A photo of our study site.
Coastal - Rocky intertidal
Trip Information
Kettle Cove Moniz 2017
Trip date: 
Tue, 2017-10-24 09:30
Town or city: 
Cape Elizabeth
Type of investigation: 
Species Survey
Time of low tide: 
Fri, 2014-10-24 08:26


Very nicely detailed evidence!