Wells Reserve at Laudholm
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Invasive & Range Expanding Species

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As the Gulf of Maine warms, some southern species are moving northward, expanding their ranges into areas that were originally inhospitable to them. Meanwhile, other species are being transported around the globe via shipping and other activities. When new species arrive in the Gulf of Maine, they may have the potential to develop into a new fishery, but they can also have negative impacts on local ecosystems. The Wells Reserve is dedicated to monitoring the arrival and spread of invasive and range expanding species through trapping and visual surveys. Additional research aims to understand the biology and ecology of these species and the impacts they may have on coastal Maine ecosystems.

Range Expanding Atlantic Blue Crabs

Atlantic blue crabs (Callinectes sapidus) are native to the east coast of the United States and form lucrative fisheries in the Mid-Atlantic and Gulf Coast regions. While their historic range is considered south of Cape Cod, MA, blue crab sightings in the Gulf of Maine have become increasingly common in recent years. During a salt marsh monitoring survey in 2020, Wells Reserve researchers found live blue crabs in the Webhannet Estuary. This prompted the start of a series of blue crab trapping surveys and research initiatives that assess the distribution, population dynamics, ecology, and impacts of blue crabs in their expanded range.

Have you seen this crab? Click the button below to report your sighting. You can also view other blue crab sightings at this site.

Report a Blue Crab Sighting

    Recent projects:

    • Trapping surveys document distribution and population dynamics in Wells, ME salt marshes (2020-present)
    • Effect of water temperature on blue crab abundance and overwinter survival (2020-present)
    • Plankton surveys quantify larval ingress into the Webhannet Estuary (2016-present)
    • Forming and leading the Gulf of Maine Blue Crab Network facilitates collaborations between researchers and resource managers (2022-present)
    • Acoustic telemetry tracks seasonal movements and habitat use in Maine estuaries (2021-2026)
    • Experiments assess interactions with local Gulf of Maine species and impacts on salt marsh pool communities (2023-2025)
    • Community scientists monitor for blue crabs in Casco Bay (2022)

    Relevant Reports & Publications:

    Crane, L.C., E.A. Burke, B.C. Gutzler, and J.S. Goldstein. 2024. Evidence of a blue crab (Callinectes sapidus) successfully overwintering in a southern Maine salt marsh. Northeastern Naturalist 31(3):N11-N16. https://doi.org/10.1656/045.031.0307.

    Media & Press:

    Contacts: Laura Crane, Research Associate

    Invasive European Green Crabs

    European green crabs (Carcinus maenas) are a major invasive species around the world and have had a substantial impact in the Gulf of Maine since the early 1900s. As the Gulf of Maine warms, green crabs have become one of the most common crab species in the Gulf of Maine. Green crabs have been implicated in declines in native shellfish species as well as habitats such as eelgrass beds and salt marshes. Research and monitoring at the Wells Reserve is aimed at better understanding local green crab populations and their impacts, improving our ability to detect and mitigate their spread.

    Recent projects:

    • Trapping surveys document distribution and population dynamics in the Webhannet Estuary (2014-present)
    • Using hemolymph color and protein concentration to detect pre-molt status and facilitate soft-shell crab production (2021-2022)
    • Evaluating the use of eDNA to detect green crabs in estuaries (2018-2019)
    • Acoustic telemetry tracks seasonal movements and habitat use (2018-2019)
    • Quantifying green crab impacts to New England salt marshes across four NERRs

    Relevant publications:

    Crane, L.C., E. Dombrowski, B.C. Gutzler, S.H. Jury, G. Bradt, and J.S. Goldstein. 2025. Hemolymph-based molt prediction in the European green crab, Carcinus maenas: potential tools for a soft-shell industry. Journal of Shellfish Research 44(1):153-161. https://doi.org/10.2983/035.044.0114.

    Zarrella-Smith, K.A., J.N. Woodall, A. Ryan, N.B. Furey, and J.S. Goldstein. 2022. Seasonal estuarine movements of green crabs revealed by acoustic telemetry. Marine Ecology Progress Series 681:129-143. https://doi.org/10.3354/meps13927.

    Crane, L.C., J.S. Goldstein, D.W. Thomas, K.S. Rexroth, and A.W. Watts. 2021. Effects of life stage on eDNA detection of the invasive European green crab (Carcinus maenas) in estuarine systems. Ecological Indicators 124:107412. Read Online | Download PDF.

    Raposa, K.B., J.S. Goldstein, K.W. Grimes, J. Mora, P.E. Stacey, and R.A. Mckinney. 2020. A comparative assessment of salt marsh crabs (Decapoda: Brachyura) across the National Estuarine Research Reserves in New England, USA. Journal of Crustacean Biology 40(1):67-76. https://doi.org/10.1093/jcbiol/ruz083

    Contact: Laura Crane, Research Associate

    Marine Invasive Species Monitoring

    The Marine Invader Monitoring and Information Collaborative (MIMIC) is a network of trained volunteers, scientists, and state and federal workers who monitor marine invasive species along the Gulf of Maine. Participants become part of an early detection network for new invasive species and help improve understanding of established invaders. Volunteers monitor sites in Rhode Island, Massachusetts, New Hampshire, and Maine. The Wells Reserve acts as the lead agency for the State of Maine and coordinates data collection efforts and Volunteers monitoring at 18 sites from Kittery to Rockland. 

    Contact: Jeremy Miller, Research Associate

    Map of MIMIC Sites

    Volunteers monitor invasives all along the coast of Maine. 

    learn more and get involved

    Related Projects

    Identifying the distribution of and interactions between range-expanding species and American lobsters

    Are range-expanding species such as blue crab and black sea bass overlapping with American lobster in the Gulf of Maine? If so, what are the interactions between lobster and novel species?