How do green crabs impact oyster farms?

We had a chance to chat with Kelsey Meyer, coordinator for the NH Shellfish Farmers Initiative and Ph.D. candidate at the University of New Hampshire. In Bonnie Brown's Ecogenetics Lab, Kelsey studies the impacts of green crabs on wild and farmed oyster populations in Great Bay Estuary. She also serves as a scientific advisor for GreenCrab.org, helping to improve our resources related to green crab ecology. 

How were you first introduced to green crabs and what made you decide to study their impact on wild and farmed shellfish populations?

I was first introduced to green crabs when working on a spat settlement project the summer before starting my PhD program at UNH. I was helping out on my advisor's (Dr. Bonnie Brown) project looking at recruitment and settlement of oyster spat on tiles throughout Great Bay in 2020. When we pulled out the cages with the recruitment tiles, I noticed there wasn't a ton of settlement of spat and that the cages were filled with green crabs. This sparked my interest in how green crabs may be affecting both wild and aquaculture oysters in the Bay.

As the NH Shellfish Farmers Initiative Coordinator, are green crabs a topic of conversation that comes up a lot in chatting with shellfish farmers and harvesters?

Based on meetings, casual conservations, and farm visits, green crabs appeared to be an issue and some oyster farmers thought they may be a nuisance. Oyster aquaculture is a sustainable and environmentally friendly industry that can move NH forward. When it comes to any type of research on this topic, it is important to gain the perspective and mindset of these farmers, as they are the ones in the field day to day and the ones directly affected. They have amazing knowledge and expertise that can greatly further research.

What is one of the most surprising things about green crabs that you’ve found in your research?

One thing I was interested in is what green crabs are consuming, in other words, could their diet affect shellfish growers. Preliminary results indicate that green crabs have a scavenger diet, and a few crabs have been identified as consuming tunicates. More samples remain to be processed, but these results are important findings as green crabs may consume biofouling off aquaculture gear. Another important preliminary finding came from an oyster-green crab interaction experiment that took place in Great Bay Estuary, New Hampshire this past Summer and Fall.  I learned that green crabs cannot break open and consume oysters unless it is a very small oyster (<1 inch) and a very large green crab (>3 inch). Statistical analyses are underway, but these preliminary findings help inform best management practices on shellfish farms and really enhance our understanding of the green crab-oyster relationship.

What steps do you think need to be taken to reduce the impact of green crabs on New England shellfish farms?

One avenue that could be taken is giving New England Shellfish Farmers grants to remove these green crabs from their farms. These shellfish farmers are not just business owners, they are also environmentalists. These shellfish farmers work hard to follow best management practices, and one way they do that is by removing potential predators, such as the green crab. Providing grants to fund these shellfish farmers to put in all the time and labor it takes to remove these invasive critters could go a long way to help keep our ecosystems healthy and sustainable.

What advice would you give to the next generation of green crab harvesters? How can current harvesters support future harvesters to promote equity and inclusion in the fishery?

Work with your local shellfish growers! Green crab harvesters should start conversations with shellfish growers to put traps around the surrounding area of their farms, this could be a potential win-win as shellfish growers would have fewer green crabs on their farms and green crab harvesters could catch a lot of green crabs and help with the prevention of green crab predation on shellfish. This could also help promote equity and inclusion by joining forces, working together, and opening the doors to future endeavors.