Mission: Green Crab

Photo by VS user sy-fy chicks
Photo by VS user Purple hippos I

Research Question

How are green crab populations changing on the Maine coast over time?

You're invited

Scientists across the state of Maine and the Northeast are working with local communities to help figure out how widespread green crabs are and what impacts they are having. Scientists think that green crabs prefer warmer waters and that they eat many native species including mussels and softshell clams. What we don’t know is if the recent increase of green crabs in the Gulf of Maine is a fluke…. or if they are here to stay.

Mission Steps

  1. Print the species card for green crab and a coastal survey datasheet.
  2. Go into the field and collect data to make your claim of FOUND or NOT FOUND
  3. If you find green crabs, take note of how many you see.
  4. If you don’t find green crabs, do you see other species of crabs?
  5. Post your data!
Photo by VS user MeowMix 2

Why this mission matters

While scientists and communities know that green crabs are invasive and disruptive, the long term impacts are still up in the air. Green crabs have been around for a long time, but the recent increase in their numbers is unusual… and worrying. Is this a short term increase, as has been the case in the past, or is the boom in their numbers the beginning of a new norm? If they are here to stay in such high numbers, how will native species respond and adapt?

By helping scientists collect this data, we all have a chance to analyze these questions and investigate the impacts of these invasive crabs!


I found 2 crabs and they had 5 spikes and they died

I found 4 crabs and killed them all

8th grade students at Blue Hill Consolidated School have been collecting baseline data about water chemistry and green crab populations in our local watershed. We investigated 3 points: Snow Natural Area, Ferry Landing, and Sherm Perkins Memorial Park. At the 3 sites, we saw a total of 59 green crabs. There were none at Snow Natural Area, 53 at Ferry Landing and 6 at Sherm Perkins Memorial Park. We would like to continue this investigation next year and hope to monitor other areas of the Bagaduce Watershed.

We personally did not find any crabs, but joined into a group where they had found crabs. We looked at the pictures that were taken and made observations based on the images. The group that we were paired with said that they had found 7 crabs along the beach on the Belfast harbor coast. While we were looking on the far side of the beach, other groups found crabs along the opposite side of the beach. It was difficult to find the green crabs because of the high tides caused by the super moon the night before. The tides the following morning where we looked were unusually high. Our location was 11 meters above sea level and 44° North and 69° West.