Seasonal Movement Patterns of an Atlantic Cod Spawning Component in the Western Gulf of Maine

Rebuilding the Gulf of Maine stock of Atlantic cod (Gadus morhua) has been much slower than expected despite substantial reductions in fishing. An improved understanding of cod movements will provide insights into their behavior and population structure, which will be useful for advising fishery managers. Since 2009, the seasonal movements of a spring spawning component in the western Gulf of Maine have been studied using conventional tags, acoustic transmitters, and archival data storage tags. During the spring, cod exhibited fine-scale, inter-annual spawning site fidelity to a coastal spawning site in Massachusetts Bay where diel, gender-based behavioral patterns were observed. Movements between multiple spawning sites were also documented. After spawning, cod moved offshore to locations that serve primarily as feeding grounds (e.g., Stellwagen Bank and Jeffreys Ledge). Cod then moved to deep offshore basins for overwintering (e.g., Murray Basin). Continued analyses utilizing tidal-based geolocation methods to estimate daily positions using oceanographic data provide additional high-resolution information on cod movements. Combining data from complimentary tagging technologies was therefore an effective approach for describing the seasonal movements of this spawning component. Our results were considered in the implementation of spawning closures, and will be helpful for informing additional management plans to support rebuilding.