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Invasives Watch | MIS Resource Center

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Marine Introduced Species Monitoring Resource Center

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.


Conduct an Invader Crab Hunt

Collecting adequate data for a particular species takes many people working together. Salem Sound Coastwatch and area high school students provided data to The Citizen Scientist Initiative: Marine Invasive Species Monitoring Organization (CSI MISMO).

Measuring a Crab's Carapace Width

After collecting crabs, you can 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.

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.



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