The Wrack

Study published in Ecological Indicators demonstrates the potential for using environmental DNA to survey green crabs in estuaries.

When green crabs arrived in New England more than 150 years ago, they found an unoccupied ecological niche in Maine’s salt marshes. Despite their long occupancy, great abundance, and serious impacts, there is a lot left to learn about green crabs. The reserve’s latest research has focused on understanding seasonal movements, population structure, sexual maturity, and effects on habitats.

Green crabs appear to have the potential to maintain their populations and continue spreading as an invasive species, even as southern Maine's coastal waters become warmer and more acidic.

Green crab burrowing activity is weakening salt marsh creek banks, causing them to erode.

We've processed all the catch from another season of trapping green crabs (Carcinus maenas) and have some preliminary results to report.

Between June and October we caught 6,432 green crabs. This is merely half the number of crabs as last year! In the figure below you can see that the catch was not distributed equally across the three trapping sites. Trends in numbers were similar to those seen last year. Again, the most crabs were caught in the Webhannet River, Wells (3,848) and the least in Broad Cove, Yarmouth (284).

I'm interested in the relationship between human communities and their environments. That is, how human activities have impacted watershed environments, coastal ecologies, and others and how environmental changes such as climate change and sea level rise are affecting human communities especially in coastal regions.

Back in September we reported on a current research project going on at the reserve — green crab sampling! We now have an update on this project, but first to refresh your memory…

Over the 2014 field season, research staff and interns participated in a green crab abundance study in hopes of getting a better understanding of population dynamics of this invasive species on marshes along the coast of Maine. We used modified eels traps baited with Atlantic herring, deployed two traps at a time per site, left them for 24 hours, and repeated this process eight times between June and October.

The invasive European green crab is not only a popular topic in the media these days; here at the reserve green crabs are receiving their fair share of attention as well — 5,878 of them so far to be exact!

The Wells Reserve has teamed up with the University of Maine, Casco Bay Estuary Partnership, and Southern Maine Health Care to study the impacts of the invasive European green crab (Carcinus maenas) on the geology and “stability” of our marshes. Over the summer we have been collecting abundance data that will later be used in conjunction with fyke net data, water quality data, and even geological techniques to better understand the effects green crabs are having on salt marshes throughout southern Maine.

The reserve works with Dr. Brian Beal, one of the leading scientists looking at the impacts of green crabs on soft-shell clam populations.

Once invasive species get into an ecosystem, it's nearly impossible to get them out.