Developing and Validating Geolocation Methods for Groundfish Species Off New England

Understanding fish movement is critical for describing spatial processes and population dynamics. Such information can improve stock assessments and fishery management plans that account for population structure, including movements across stock boundaries. Archival electronic tags present the opportunity to acquire higher resolution data on fish movements. Geolocation methods have been commonly used to estimate daily positions of pelagic species using light, temperature, and depth data. However, the development and validation of alternative methods is required for geolocation of demersal species. Therefore, we developed geolocation methods for New England groundfish (Atlantic cod and yellowtail flounder) using Hidden Markov Models (HMMs). Geolocation estimates focus on modifying the observation likelihood and behavior models of an existing HMM framework to address region- and species-specific applications. We performed validations using a comprehensive quantitative skill assessment process relying on stationary tags, double-tagged fish (archival tag and acoustic transmitter), and simulated tracks. The developed geolocation methods are expected to improve our understanding of the spatial dynamics of cod and yellowtail flounder, which will be helpful for future stock assessments and fishery management plans. The developed methods are also applicable to other groundfish species and regions.