Have you ever seen a sand crab at the beach? If not, imagine little creatures with grey shells that wiggle backwards and live underneath the sand. You may ask yourself, why should we care about some tiny sand crabs? Well the answer is simple, they are actually very important to a beach’s ecosystem, as they are the basis of the food web. By monitoring sand crabs, we can indicate the health of the entire beach.
The mating season of the Pacific sand crab occurs from February to October. The female sand crabs are able to produce up to 45,000 eggs and carry them on her abdomen. These eggs take about 30 days to develop and after they hatch, the newborn sand crabs drift in the ocean as planktonic larvae for approximately 4.5 months while they go through 8-11 larval stages. Once these small sand crabs return to the shore, they are considered “recruits”. Although recruitment can occur year-round depending on environmental conditions, most recruitment occurs in spring, early summer and again in the fall. Based on the information given in the article, there should have been an abundance of recruits during the September trip to Ocean Beach. However, there were more males and females than there were recruits. According to our school’s data from past trips, this pattern has been the same since 2003.