Marine Introduced Species Monitoring Resource Center

Join in the Invader Crab Hunt

Collecting adequate data for a particular species takes many people working together. This is one reason students and their teachers are being asked to join the Citizen Scientist Initiative: Marine Invasive Species Monitoring Organization (CSI MISMO). Here are some of the things you will learn and how you can be part of scientific research project in the Gulf of Maine being conducted by Dave Delaney, McGill University.

Measuring a Crab's Carapace Width

After collecting crabs, you will measure each crab shell at the widest section of carapace. If crabs are less than 5 mm or too small to measure, indicate that it is too small to accurately measure by putting a ? in the size column on the data sheet.

Asian shore crab
(Hemigrapsus sanguineus)

green crab
(Carcinus maenas)

Determining Sex of Crabs

You will be asked to record the sex of each crab that you measure. You can determine the crab's sex by looking at the underside of the crab's carapace. The shape of the abdomen or tail flap is different for males and females. The male has a thin triangular apron, while the female's is larger and rounder. Sex of young juveniles may not be decipherable. Male Asian shore crabs can also be identified by the presence of a bulb-like structure on the inside of the pincer claws.

Mark/Recapture Study

Under the guidance of Salem Sound Coastwatch staff, high school students have been banding Asian shore crabs and green crabs. The information they collect will be used by Dave Delaney of McGill University in his research to develop a population/spread model to predict expansion of marine aquatic invaders, in particular the European green crab and Asian shore crab.

Using pliers and metal rings to band Asian shore and green crabs.

Banded Asian shore crabs being released one meter from trap.

Minnow trap secured and baited with cat food ready
to catch crabs. We will retrieve the trap in 24 hours.

Click here for more information on how to become involved in CSI MISMO and to monitor for crabs in New England: Find the invasive crabs and help the scientists.

For Students and teachers: By being citizen scientists, students will

  • effectively learn about the process of science, in the best manner—by doing it;
  • heighten the their public awareness regarding a critical issue for biology and environmental science;
  • build their confidence in their abilities and offer valuable experience for budding scientists;
  • broaden the impact of a science and math curricula beyond a traditional academic setting that is engaging and enriching due to its applicability in the real work;
  • be collecting data serve a purpose since it will be used in publishable research currently being conducted by graduate students, university professors, and government scientists. If done properly, it will be mapped and posted on the MIT Sea Grant website.

Nab the Aquatic Invader! Be a Sea Grant Super Sleuth

This aquatic invasive species national education site asks students in grades 4–6 (or just starting to investigate invaders) to become Junior Detectives or students in grades 7–10 (or those who want a bigger challenge) to become Super Sleuths.

Species Identification Resources

Monitoring Methods/Data Sharing

MIS Resource Center Home


Scientific Books and Papers

Additional Web Site Links



Since 1991


Salem Sound

201 Washington Street
Suite 9
Salem, MA 01970

Save to Bookmarks