Mole Crab "Baby Boom"

Student Scientists Detect Mole Crab “Baby Boom” on Sanctuary Beaches

For the first time since 2003, tiny Pacific mole crabs (Emerita analoga), called recruits, are settling onto Sanctuary beaches in large numbers.

In the past weeks, students from middle and high schools throughout the Bay Area have investigated mole crab populations on Farallones and northern Monterey Bay marine sanctuary beaches as part of the LiMPETS (Long-term Monitoring Program and Experiential Training for Students) program.

Many of the beaches monitored by LiMPETS appear to be experiencing this recruitment event, but one beach has stood out in particular: students from Pescadero High School found over 1500 mole crabs, almost all of them recruits, in their samples taken on Pescadero State Beach in late April. That translates to an abundance of about 1600 crabs per square meter of beach!

Students are recording the extent of this unusual recruitment event and data is being archived in the LiMPETS long-term database. Why this recruitment is occurring now after so many years with little to no recruitment is a difficult question to answer. Some scientists theorize that El Niño events contribute to spikes in recruitment. Mole crabs spend approximately 4 months as pelagic larva, drifting with ocean currents often far out into the open water. During El Niño years, these currents slacken and larval mole crabs remain close to shore, allowing them to return to our sandy beaches easily once it’s time for them to settle.

LiMPETS is an environmental monitoring and education program for students, educators, and volunteer groups. This hands-on program was developed to monitor the ocean and coastal ecosystems of California’s National Marine Sanctuaries to increase awareness and stewardship of these important areas.

Two distinct monitoring programs make up the core of the LiMPETS network: the Rocky Intertidal Monitoring Program and the Sandy Beach Monitoring Program. Both programs are designed to provide students with the opportunity to experience the scientific process firsthand. Through research-based monitoring and standardized protocols, students develop their problem solving skills, gain experience using tools and methods employed by field scientists, and learn to analyze data.

To find out more about the LiMPETS program, visit: www.limpetsmonitoring.org.