GABRIELA M. BRADT PhD
FISHERIES SPECIALIST - NH SEA GRANT/ UNH COOPERATIVE EXTENSION
The New Hampshire Green Crab Project has been in existence since the summer of 2015. It began as a side project and internship for NH Sea Grant and UNH Cooperative Extension after I asked why we didn’t just “eat the invasive” like what was happening with lionfish in the south. Also, like in the south, why couldn’t we create a soft-shell crab industry with a seemingly endless supply of green crabs? Knowing that the blue crab has a tell-tale morphological sign to indicate that the crab will soon molt and be a “soft-shell”- the desired product for the market- I set out to find a similar morphological clue for green crabs. This was the initial objective and goal for the project- to figure out when the crab would molt so that they could be harvested as soon as they were soft-shells. The first attempt at this proved much more difficult to achieve as we did not realize that males and females do not molt simultaneously and that neither sex molt at the height of summer- which was when my intern was working on this project. However, all was not lost, as the information we gathered through trial and error led us to streamline our project, refine our questions and timelines.
During the summer of 2016- realizing that we had likely missed the optimal time for male green crabs, we focused on narrowing down the female peak molting time as well as continued to track individual crabs and scrutinized them for any morphological indication that they would soon molt. While we were able to get 81% of the crabs to molt, with an average of 23 days from capture to molting, we were still not successful in observing any morphological molting indicators. Other important observations for females included:
• Temperature range with the most molts: 20.1°C-20.6°C: N=8
• All molt events occurred at temp range: 19.1°C-22.5°C
• All molt events occurred between: 9/9/16-9/24/16
• Female “autumn” molt window-influenced by temperature and daylight.
• Mid-September yielded the most molting events.
• Molting size range: 39-51mm, average molt size 48 mm
• No discernible morphological signs to identify “busters”
Currently, with new collaborators and information about that “elusive” morphological indicator- the NH Green Crab Project has evolved and expanded to include male green crabs and citizen science monitoring program in order to track the male crab molting peak. Using crowd-source mapping technology, data and pictures of males green crabs between 1.0-2.3 inches wide, are submitted via this form and the data are automatically incorporated into a map showing the different locations and dates as well as pictures. This component of the project will get citizens of all ages involved and awareness will increase about the potential for these crabs to be controlled through monitoring, harvesting soft-shells and increasing interest and demand in eating a new type of local seafood product.
Dr. Bradt has also been heavily involved in outreach and education, leading green crab sessions at the Maine Fishermans Forum, hosting citizen science events, and organizing Portland's first Green Crab Working Summit. To learn more, visit the New Hampshire Green Crab Project's page.
Interested collecting green crab data in your local area? Visit her green crab guide below.