Invasive SpeciesGreen crab

Carcinus maenas
FOUND by apealingbananas
Cape Elizabeth
ID Confirmed
Quality checked by Mrs. Moniz
Peer reviewed by flamingtoucans
Field Notes
It was the beginning of fall when we were at Kettle Cove Beach. I saw and learned several new exciting things. The temperature was about 55 degrees.The weather was foggy and the air was moist, the gray skies made it cool, but warm enough so we didn't need our winter jackets and hats. It was low tide at 8:30 in the morning. I wasn't surprised to see all of the green crabs, however I was sad to see all of the Asian shore crabs, because they are a generally new invasive species. I see the calm waves on the water. I hear my classmates talking and laughing, and I hear the cackling of seagulls. I smell the salty sea and the stench of the moisture in the air. The whole expedition went smoothly because everyone was just happy to be out of school on this perfect October day in Cape Elizabeth, Maine.
A sketch of our study site.
Supporting Evidence
Photo of my evidence.
Our first piece of evidence is based on the shell size of the crab. The Vital Signs identification sheet says that the normal adult green crab has a shell the size of about 10cm wide (from side to side). As seen in the picture our crab does have a shell size of about 6 cm which is almost 10 cm. It could not yet be full grown crab which explains why it isn't quite 10 cm.
Photo of my evidence.
The identification card on the Vital Signs website says that the green crab has a distinguishable pentagon shaped shell. The specimen that we discovered also had a pentagon shaped shell that you can see above. Our crab doesn't have a rectangular shell which means it isn't the Hairy Clawed Shore Crab. I know this because the Hairy Shore Crab has a rectangular shell according to the Vital Signs identification card.
Photo of my evidence.
According to the Vital Signs identification card the green crab has five spines running down each side from its eye to its claw, and the crab we found has five spines as well. This proves that the specimen we found is not another species because local crabs have more than six spines, Asian shore crabs (an invasive species) have three spines, and Chinese mitten crabs (another invasive species) have four spines.
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 43.562176 °
W -70.219148 °
Observation Site Information
A photo of our study site.
Coastal - Rocky intertidal
Trip Information
Kettle Cove Cape Elizabeth
Trip date: 
Tue, 2014-10-28 09:08
Town or city: 
Cape Elizabeth
Type of investigation: 
Species Survey
Time of low tide: 
Tue, 2014-10-28 08:25


Those are some great notes! I like the arrows pointing to the spines.

Agreed! That's also a beautiful sketch!