The diet of the Asian shore crab is varied. In the early 1990’s it was believed that the crab was herbivorous. However, in 2000, a researcher from the University of CT found that the crab was eating both animal and vegetable material in almost equal amounts. It was also discovered that the crab had a wide latitude of beach area for its habitat. It has survives throughout all of the intertidal zones clear out to deep water. Today (2009) these crabs can even be found on the deep pilings in harbors. How many crabs are there? When the Shore Crab was first noticed on the rocky beaches of Long Island Sound, there was an estimate of 8 to 10 crabs per square meter. That number increased to 80 crabs per square meter by 2005. The student data from this investigation shows a population of around 36 crabs per square meter based on surface observations. Student Investigations These crabs are a good species for student investigations because they are small, numerous and easy to identify. Since the crabs live under rocks that are about eight inches by eight inches it is easy for students to locate their rocky homes and overturn the rocks. Students follow the method established for population field studies: a square meter grid is set out on the rocky beach, a diagram of the square meter grid is drawn on paper showing all of the rocks in the grid. One by one the rocks are overturned and the crabs are counted. One student turns the rock and two students observe carefully to count the crabs. A fourth student fills in the data sheet.
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