Objectives: OBJECTIVES: This proposal is focused on developing and applying methods for integration of electronic tagging information into stock assessment of large pelagic animals. Since a relatively large amount of information exists for Atlantic bluefin tuna (Thunnus thynnus) this species will serve as a test case. Our objective is to expand likelihood-based techniques for improving estimates of migration, mortality and recruitment of large pelagic species in stock assessments. This will be done using a combination of electronic and conventional tagging datasets for Atlantic bluefin tuna (Thunnus thynnus) and other species if available. Necessary tools to evaluate performance of alternate management regimes will be developed. Methodology:METHODOLOGY: Spatially structured population models will be fit to information returned from pop-up satellite archival tags (PSATs) and conventional tag data as well as the fishery data used in the current stock assessment. Utilizing available archival and conventional tag information will help develop better estimation of fishing and natural mortality, as well as movement estimates between management areas. Since spatially structured population models explicitly estimate mixing and movement between stocks, efficacy of alternative management regimes may be easily evaluated using this approach. We propose using advection diffusion reaction (ADR), finite state continuous time (FSCT) and biophysical mixed effects models to achieve these objectives. Rationale: RATIONALE: Electronic tags, especially implanted archival and pop-up satellite archival tags (PSATs), have been valuable tools for determining basic aspects of life history, horizontal and vertical movement rates, stock boundary determination and assessing mixing rates between stocks but current population dynamics methods fail to fully utilize the movement information returned. Much of the impetus for tagging large pelagic and other fishes with electronic tags is predicated on usefulness to stock assessment and population dynamics. The challenge is that horizontal and vertical movement data are not easily integrated into current frameworks typically used to assess mortality, spawning stock biomass and recruitment. Due to the scientific necessity for better informed stock status, Atlantic bluefin tuna would serve as an excellent test case to develop methods towards integration of these types of data into population assessment. The methods developed may also be applied within any fishery where electronic tagging occurs.