Warming Waters Bring Marine Invasion

On April 11, 2022, Dr. Marissa McMahan, Director of Fisheries at Manomet, gave a virtual presentation on one of the consequences of the warming Gulf of Maine – an increase in numbers of the invasive European Green Crab (EGC). The presentation was co-sponsored by CREA and Green Steps, a group that promotes environmental stewardship and education. The speaker was introduced by Dr. Jed Fahey, a member of both CREA and Green Steps.

Looking back, decades ago, Maine had diverse and productive fisheries – small-scale, seasonal fisheries (shrimp, scallops, cod, halibut, clams, etc). Today, 79% of Maine’s fisheries is comprised of a single species – lobster – which is the only product for many fishers.

The Gulf of Maine is warming faster than 99% of the world’s oceans and this warming is affecting our coastal waters. Cold water species such as shrimp, cod, and the plankton that support key species are moving north, warmwater species are moving into the Gulf of Maine, and invasive species are thriving.

Invasive species  are characterized by the following characteristics: they cause ecological and economic damage; they adapt and reproduce quickly; they outcompete native species; and they have few or no predators.

In the past, populations of the EGC did not thrive in Maine due to the cold winter water, but that is changing and their numbers are on the rise. They are voracious predators of shellfish, oysters, mussels, and more; they destroy eelgrass and saltmarsh habitat; and they compete with native species for food and shelter.

Unfortunately, they are here to stay, so – as Marissa noted – “If you can’t beat ’em, eat ’em!” Italy has a lucrative fishery for EGC, so researchers and fishers in Maine are working to develop one here. There are challenges, but early results suggest potential for a lucrative market in Maine.

Timing the catch to when crabs are molting, and storing them while waiting for the molt are just some of the challenges. A bigger challenge is what to do with the by-catch (crabs that aren’t molting), as fishers are prohibited from throwing invasive species back once caught. The hope is that markets for products like compost, dog food, chicken food, etc will develop.

Watch the video of Marissa’s presentation below for much more information about how researchers, fishers, and volunteers are coming together in search of innovative solutions to this ecological and economic challenge. Another reason to do everything we can to roll back climate change!

For information on how to identify invasive crabs, download this document.