Date of Award

Spring 2023

Project Type


Program or Major

Biological Sciences

Degree Name

Master of Science

First Advisor

Nathan B Furey

Second Advisor

Jason S Goldstein

Third Advisor

Elizabeth L Harvey


The green crab (Carcinus maenas) is a long-term invader of the Northwest Atlantic that negatively impacts coastal ecosystems and is a growing concern for management. However, spatial metrics of use have not been robustly quantified, and the general movement ecology is still generally lacking for this invasive species. We tracked the meter-scale movements of 43 green crabs using acoustic telemetry via a Vemco Positioning System (VPS) within the Webhannet estuary (Maine, USA). From the 163,307 crab positions yielded from the VPS array from May 27 – December 16, we described a suite of movement ecology metrics including individual crab position in the estuary, movement rates, and home range sizes estimated using Brownian Bridge movement models. Key covariates of movement were identified using Generalized Additive Mixed Models (GAMMs). Tagged crabs had highly variable home range sizes and used a core use area that was <1% of the total potential habitat covered by the VPS, suggesting that their impacts are localized and acute. Tagged crabs were mostly located in the central area of the estuary and moved at a rate similar to other benthic crustaceans. Ovigerous females had mean estuary positions that were significantly downstream when compared to those of non-ovigerous females, and days-to-hatch, estimated from in situ egg development observations, was retained in top ranking models for estuary position. Sex and ovigery were consistently retained in top-ranked models as important covariates of movements, and other covariates including month, water temperature, and lunar illumination were retained and highlighted how changes in movements were influenced on a variety of temporal scales. Overall, these findings fill key knowledge gaps in green crab ecology and invasion biology and describe how movements can be affected by biology and influenced dynamically by covariates at diel to seasonal scales. Furthermore, these findings help to better inform management practices and modeling efforts, such as the targeted removal of ovigerous females near estuary mouths and improving regional larval dispersal models, to better understand and mitigate negative effects of this invasive species on estuarine environments around the world.

Available for download on Wednesday, September 25, 2024