Blue crabs are fascinating animals and studying blue crabs you can learn about biology and ecology as well as mathematics. You can download our set of blue crab education hand-outs (pdf) and the research data files below for classroom activities.
Using Research Data Files: a Student Activity
To study the population of the blue crab in the Chesapeake Bay over time, SERC researchers regularly go out with a research vessel to collect crabs with a trawl, a large conical net that is dragged along the sea bottom.
In this activity, students will use data from SERC's 1998 trawling season to get a better understanding of changes in the crab population throughout the year.
The Research Data File (PDF) contains a collection of blue crab data collected during the 1998 trawling season. The file includes information for three months: April, June, and September. Each month, three trawls were performed at the Dock Mud Station. The collected crabs were measured and their sex (male, adult female, or juvenile female) was determined.
Plotting the Data
Using the blank graphs (provided below) students can plot the research data. You can combine all the trawling data for each month (n=60), which will give your students a substantial sample to work with. This will help the students see changes in the population throughout the year. i.e., in April the crabs are fairly small and males and females are evenly distributed; in June the average size has increased and the number of adult females has increased; and in September, the crabs are substantially larger and the number of adult female crab population is at its peak.
Here are the blank graphs that you can use to either record the number of blue crabs of a certain sex or of a certain size collected during the trawls. You can print those and copy them for your students.
Students can also analyze the data to calculate such characteristics as mean size for all crabs or for each group of crabs.