Using Acoustic Telemetry to Map Atlantic Cod Spawning Activity and Inform Fishery Management in the Gulf of Maine

Rebuilding the Gulf of Maine stock of Atlantic cod (Gadus morhua) has been much slower than anticipated. Many historical spawning components have been depleted, which has reduced stock productivity and stability. In response, fishery managers have implemented closures to protect cod spawning aggregations. The spatial and temporal extent of these closures have changed over time because of scientific uncertainty and to allow fishing for other species. The objective of this project is to characterize the spatial and temporal distribution of cod spawning activity during the winter in Massachusetts Bay and western Stellwagen Bank, western Gulf of Maine. Spawning cod were tagged with acoustic transmitters (n=317) and tracked during three consecutive winter spawning seasons from October 2013 through March 2016. Tagged fish were tracked using acoustic receivers deployed as part of stationary receiver arrays or mounted on underwater gliders that traversed putative spawning areas. Preliminary results suggest that peak spawning occurred from November through January. Spawning site fidelity was documented, and multiple ‘hotspots’ were identified as areas where tagged cod were aggregating, including some evidence for inter-annual variability in timing. Results have been helpful for identifying habitat use by spawning cod, which will be valuable for informing future fishery management measures.