Daniel Goethel – MIT Sea Grant – NMFS Population Dynamics Sea Grant Fellowship: A more realistic assessment of yellowtail flounder using spatial aspects of population dynamics

Objectives:The goal of this research is to provide a more realistic assessment model of yellowtail flounder, Limanda ferruginea, which takes into account the spatial aspect of population dynamics, thereby avoiding closed population assumptions inherent in current assessment models. The research will be carried out within three main modules: 1. A spatially explicit, tagging-integrated stock assessment model that allows adult movement and incorporates tagging data directly within the objective function; 2. An Individual Based Model (IBM) that assesses the degree of mixing between sub-populations during early life history stages; 3. A full life history model that includes a component in the objective function that fits to IBM results in order to help inform recruitment.Methodology:Modeling of the adult movement model and the full life history model will be carried out using the AD Model Builder (ADMB) programming language. The IBM will be run using the FORTRAN modeling language that is linked to the outputs of the Finite Volume Coastal Ocean Model (FVCOM).Rationale:The proposed research will enhance the field of stock assessment and the study of population dynamics by increasing the general knowledge of how spatial processes in the marine realm affect subpopulation dynamics. The development of methods will enhance stock assessment by developing a generalized model that allows for adult movement and directly incorporates tagging data into the objective function, and is geared towards demersal species that demonstrate random movement and often have coarse data. This will be one of the first spatially explicit models developed primarily for these species. The IBM will help to advance the understanding of spatial recruitment processes and how oceanographic and atmospheric processes can alter recruitment rates. Finally, the full life history model will provide one of the first quantitative meta-population models developed within a stock assessment framework. Most importantly, this research will provide a new and more realistic technique to assess yellowtail flounder stocks. Hopefully, improved science will lead to better management and productive stocks, thus returning yellowtail to prominence as one of the most commercially important species in New England, which it has been for almost a century.