Graduate students Bethany Johnson and Nicholas Grunloh have been selected for the 2019 NOAA National Marine Fisheries Service-Sea Grant Fellowship.
Johnson and Grunloh are among eight recipients of the population and ecosystem dynamics fellowship awarded nationally through a competitive selection process. The program supports students pursuing doctoral degrees in population and ecosystem dynamics, as well as marine resources economics. The two-year fellowship is a focused workforce development effort to train professionals in the highly specialized field for NOAA’s science-based approach to fisheries management and living marine resources.
Johnson is a Ph.D. student studying applied mathematics in the context of fisheries management. She graduated from Sonoma State University with a bachelor’s degree in applied and pure mathematics in 2017. Her research focuses on forecasting harvested populations from the California current ecosystem.
Although many fisheries are successfully assessed with traditional age-structured models, short-lived species in variable environments, such as market squid and the Pacific sardine, are hypersensitive to recruitment fluctuations. In order to accurately predict the populations and identify optimal harvest limits, recent studies have suggested empirical dynamic modeling may be a reasonable alternative to the conventional models.
As a fellow, Johnson will evaluate the feasibility and effectiveness of using empirical dynamic modeling for the assessment and management of short-lived marine species in the California current. She aims to test the prediction accuracy of empirical dynamic modeling for six commercially valuable, short-lived species and use empirical dynamic programming to derive near-optimal harvest control rules for each stock. She will then improve the performance forecast by including spatial information.
This research will advance fisheries modeling in general and will, in particular, help improve NOAA's ability to accurately forecast the dynamics of economically valuable, highly variable species.
Grunloh (B.S., '12, marine biology) is a Ph.D. student studying statistics and applied mathematics. He works as a statistician at the NOAA Southwest Fisheries Science Center in Santa Cruz. His research interests include questions at the intersection of Bayesian statistics and quantitative fisheries management.
Fisheries managers use stock assessments—collections of demographic information about fisheries populations—to determine the health of the population and inform fisheries management. Modern stock assessments use models to compile data from different sources to inform management decisions about fish populations. The decision-making process, based on these models, can be simulated and evaluated via a process called Management Strategy Evaluation (MSE). Presently there is no clear, objective, and practical way to determine how competing sources of information should be weighted in stock assessment models.
Grunloh will use Bayesian optimization methods together with MSE simulations to evaluate and optimize the effectiveness of stock assessment models with respect to how data sources are weighted. He aims to test these methods against existing assessment models of rockfish populations which live along the California coast.
This research builds upon the most current methods of data weighting, and is novel in its use of simulation together with efficient optimization algorithms to objectively calibrate stock assessment methods. Using these methods, he hopes to provide stock assessment scientists with tools to better serve population health and better inform management objectives.
The joint fellowship program has supported 100 population and ecosystem dynamics students and 36 marine resource economics students since its inception. Ninety-five percent of alumni remain in their field of study after completing the fellowship program.