Modeling in an integrated ecosystem research framework to explore recruitment in Gulf of Alaska groundfish – Applications to management and lessons learned

Abstract

The Gulf of Alaska Integrated Ecosystem Research Program (GOAIERP) supported multi-disciplinary analyses integrating physical and biological oceanography and modeling to examine how the environment influences survival and recruitment of early life stages of select commercially and ecologically important groundfish species. Recruitment is an important component of population variability, and understanding the processes influencing recruitment is central to fishery management and ecosystem planning. Determining the relative impact of advection and the environmental conditions experienced during transport between spawning and nursery areas is an inherently interdisciplinary problem. It requires consideration of physical and lower trophic level environments in concert with early life history dynamics. Here we discuss how Eulerian ecosystem models and Lagrangian Individual-Based Models for groundfish were integrated within the framework of an interdisciplinary observational program. Metrics (e.g. regionally-based averaged water temperature, integrated primary production, probability of juvenile settlement) were derived from model outputs as proxies for recruitment success. The recruitment indices were then correlated to estimated recruitment from stock assessments. Using the GOAIERP as a case study, we discuss the value that modeling can add to a field program and fisheries management planning, the challenges faced, and steps that can be taken to maximize program success. Coordination of model development, experimentation, and field sampling is necessary but can be challenging. Consideration of the appropriate sequence during data analyses and model development is critical. Careful consideration must be given to ensure that data collected in the field will inform, improve, or validate models. Sufficient time must be allocated within the program to incorporate field data collected during the program and mechanistic understandings into the models. Model outputs should be designed to have utility to management decisions and value to regional stakeholders. Collectively, the studies in this modeling program provide insight as to how models might be used to better understand recruitment processes and lead to recommendations to support the integration of ecosystem models into fisheries management.