Using Unmanned Aerial Vehicles for the study of eelgrass habitat

Eelgrass (Zostera marina) is ecologically important in nearshore Newfoundland ecosystems as it provides sheltered habitat for juvenile fish, such as Atlantic cod (Gadus morhua). However, the recent invasion of green crab (Carcinus maenas) to the southern and western coast of Newfoundland is threatening eelgrass density. The current project is the first to use Unmanned Aerial Vehicles (UAVs), also known as “drones”, to assess the density of eelgrass (Zostera marina) beds in the nearshore waters of Newfoundland to provide a foundation for future eelgrass density monitoring projects. In addition, Fukui traps were used to determine a relative density of green crab in each area surveyed to be able to see how future green crab and eelgrass density may correlate, as well as to test whether modified Fukui traps with a slightly wider entrance slit are more effective than unmodified Fukui traps to assist in green crab removal projects. The drone provided an effective way to survey eelgrass density with the photo-stitching software Pix4Dmapper, and optimal conditions for flight were identified. In addition, modified Fukui traps caught 62% more green crabs than unmodified traps, which demonstrates that the modified trap opening should be used in removal programs. In conclusion, the drone survey method proved to be a promising new addition to eelgrass survey research to be able to trace the progression of eelgrass density decline in Newfoundland. Furthermore, there is the potential for further testing and implementation of the modified Fukui traps for green crab removal projects.