Native SpeciesJonah crab

Cancer borealis
FOUND by pbernhardt
ID Confirmed
Quality checked by chotaling
Peer reviewed by
Field Notes
It was a beautiful day and we went out with a group aboard the LUCKY CATCH. Our group was assigned to do a species survey with trap #1. The traps had been out for 3 days and baited with herring. Our task was to focus on one species, Jonah Crab. We were able to choose the species our group wanted to look for. Overall the group was going to do a total count of invasive species verses native species across the total number of 4 traps. We sampled a rocky bottom habitat. We were delighted to be in the ocean harbor ecosystem and saw gulls, and seals.
A sketch of our study site.
Supporting Evidence
Photo of my evidence.
We had an oval carapace that measured 10cm in width. That is consistent with the species card for Cancer borealis. Th carapace has a rounded dome look to it with rounded spines. Again this is consistent with the species card.
Photo of my evidence.
The crab we looked at has 8-10 rounded spines from eye to the side of the shell. This matches the species card for the Jonah crab aka Cancer borealis. Also this species has a purple spots and the rock crab which is similar does not.
Photo of my evidence.
This crab has a muscular claw and yellowish color on the underside. This evidence is found on the species card for the Jonah crab, Cancer borealis. The fun name for this crab is the sleepy crab. We compared this evidence to the similar native species rock crab.
Species Observation: Species Looked For
Did you find it?: 
I think I found it
Scientific name:
Cancer borealis
Common name:
Jonah crab
Sampling method: 
Photo of our sampling method.
Place Studied
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Map this species
N 43.639550 °
W -70.211450 °
Observation Site Information
A photo of our study site.
Coastal - Dock
Trip Information
Casco Bay
Trip date: 
Tue, 2012-08-14 09:00
Town or city: 
Type of investigation: 
Species Survey
Time of low tide: 
Tue, 2012-08-14 03:22


You did a great job identifying this crab! One other feature that you probably noticed is that the spines on the Jonah crab are each very jagged, unlike the rock crab's spines which are smoother.