Invasive SpeciesGreen crab

Carcinus maenas
FOUND by taiga
ID Confirmed
Quality checked by Josh C
Peer reviewed by Josh C
Field Notes
I was happy because I was the air was clean and it was bright outside. I saw the Passagassawakeag river and seaweed and smelled a very fishy scent since it was lowtide. I am surprised by what I found because we found more crabs than I was expecting. A question I ran into was why were all the crabs green, and why were they all very small?
A sketch of our study site.
Supporting Evidence
Photo of my evidence.
We used the Green Crab Identification guide to determine that the crab we found was indeed a green crab.
Photo of my evidence.
By looking at the underside of the crab as shown in the picture, we were given more eveidence to support our assumption of us finding a green crab.
Photo of my evidence.
The overall color of the crab that was found and the ridges around the sides of the shell gives away the fact that it is a green crab.
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 44.428000 °
W -69.003900 °
Observation Site Information
A photo of our study site.
Coastal - Rocky intertidal
Trip Information
Belfast Maine Boat Waterfront II
Trip date: 
Thu, 2016-12-08 13:22
Town or city: 
Type of investigation: 
Species Survey
Time of low tide: 
Thu, 2016-12-08 11:06


Nice job on your identification. Do you know how to tell if the crabs you found were male or female? The picture of the crab that you took that is on it's back getting measured is a male crab. See if you can figure out how to figure this out on your own!

You are right! It is a green crab, but what pieces of evidence from the ID card did you use to figure that out? Remember that color can vary so that's not always the best feature to use to make your identification.

Thanks for your great questions. As for the color, give some thought to the habitat(s) where you found the crab and where you know it lives. Why might it have a greenish color?

And about the size... sounds like you may have found crabs that are all from the same year class, that is, they were all born at the same time.