Invasive SpeciesCommon periwinkle

Littorina littorea
FOUND by Purple Periwinkle
Cape Elizabeth
ID Confirmed
Quality checked by Ms. Moniz
Peer reviewed by Moody Teenagers
Field Notes
We step off the bus. Immediately the wind rushes past us and we can hear it whistling in our ears. The smell of salty seaweed envelopes us as we step down the rocks to go nearer to the wet intertidal rocks, where we know Common periwinkles are usually found. The time is 9:17 AM on October 24, 2017. From the research we did before we went to Kettle Cove, we know it is flood tide, meaning the tide is coming up. There are some boats bobbing in the water far away from shore, and the cloudy day we were having only helped to make the boats become more easily seen. We are at Kettle Cove to find the invasive species Common periwinkle and document it for the vital signs website. We immediately find the specimen without any trouble. It was located near seaweed and next to another periwinkle, both of them clinging onto a rock.
A sketch of our study site.
Supporting Evidence
Photo of my evidence.
We believe we found the species common periwinkle. The common periwinkle has a white lip and dark purple and brown shell. As shown in the photo, the specimen has both. The shell itself of the common periwinkle is also thick and smooth. The periwinkle in the picture also has a thick and smooth shell.
Photo of my evidence.
Another reason that we believe that we found the common periwinkle is that common periwinkles always have a short spiraled end. The periwinkle in the picture does too. Common periwinkles can also grow up to four cm, so the periwinkle shown in the picture fits the description, as it is two centimeters.
Photo of my evidence.
Common periwinkles can often be mistaken for rough periwinkles. A feature that sets the common periwinkle apart from the rough periwinkle is its flattened whorls. The whorls are the spiral on the bottom of the periwinkle in the picture. The rough periwinkle has deep indented whorls. The common periwinkle in the picture has the flattened whirls as described.
Species Observation: Species Looked For
Did you find it?: 
I think I found it
Scientific name:
Littorina littorea
Common name:
Common periwinkle
Sampling method: 
Just looking around
Photo of our sampling method.
Place Studied
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Map this species
N 43.561100 °
W -70.217500 °
Observation Site Information
A photo of our study site.
Coastal - Rocky intertidal
Trip Information
Kettle Cove
Trip date: 
Tue, 2017-10-24 09:30
Town or city: 
Cape Elizabeth
Type of investigation: 
Species Survey
Time of low tide: 
Tue, 2017-10-24 08:26


That a wonderful way to undeniably document the size of a specimen.