Category Archives: Clam ecology and biology

The Green Crab Lifecycle

European Green Crab

European green crab (c) Can Stock Photo / mikemols

The European green crab (Carcinus maenas) arrived in the New York and New Jersey ports in the early 1800s, spread to Casco Bay by the 1890s, and continued to spread northward to Downeast Maine and the Bay of Fundy over the twentieth century (Fulton et al., 2013).  It is a voracious predator, but until recently the crab’s numbers in Maine were kept in check by cold winters. That was enough to make it possible for softshell clams to continue to thrive even though green crabs were eating them. All that has changed now that winters are warmer. Research by Dr. Brian Beal of the Downeast Institute, along with others (Beal, 2006; Tan & Beal, 2015), makes a strong case that the green crab has contributed substantially to declines in softshell clam populations in many parts of Maine.

Because CSI-Maine is designed to provide Maine communities with information they can use to protect clams from predators, knowledge about green crabs and their lifecycle is useful in interpreting the data we collect and in thinking about new approaches to increasing and sustaining the clam harvest. Continue reading

The Clam Lifecycle

Small clam being measured

Collecting data about clam shell length.

There are many reasons that it will be useful for students to have an understanding of the softshell clam (Mya arenaria) life cycle as they work as part of CSI-Maine. It will help them understand when clams are most vulnerable to predators, how long it takes for a clam to reach legal size, why there can be lots of seed clams even in areas where there are no adult clams, and much more. Understanding the clam lifecycle will also be important for using CSI-Maine in support of learning goals related to ecological concepts such as predator/prey relationships and population dynamics.  So … here is a “very short course” on the topic. Continue reading