Graduation Date

Fall 2021

Document Type



Master of Science degree with a major in Natural Resources, option Fisheries

Committee Chair Name

Dr. Eric Bjorkstedt

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Dr. Andre Buchheister

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Dr. Christine Cass

Third Committee Member Affiliation

HSU Faculty or Staff

Subject Categories



Individual-based models (IBMs) have emerged as a powerful tool for ecological research and are particularly well suited to studies of plankton ecology. In this thesis, I develop an IBM for the North Pacific krill, Euphausia pacifica, with the goal of replicating observed variability in size-structure in the northern California Current Ecosystem. Krill, and E. pacifica in particular, are central to the structure and function of the California Current Ecosystem. Their response to environmental forcing translates climate variability to higher trophic levels and underpins broader ecosystem responses. Recent observations indicate environmental and climate-related shifts in E. pacifica size distributions, which have important implications for understanding krill production dynamics and ecosystem interactions. I advance existing IBMs for E. pacifica by enabling temperature-dependent maturation and incorporating other observed relationships that were not captured in published models. I used a pattern-oriented modeling approach to develop a model capable of resolving realistic size and growth dynamics. Patterns in model output were compared to population size distributions from field-based observations off northern California. Modifications to the model were incorporated based on discrepancies between model output and field observations. The resulting IBM represents a clear advancement toward obtaining accurate predictions of E. pacifica growth and size dynamics. The model captures seasonal and interannual patterns in growth and size across most life history stages. In addition to size dynamics, model-generated development, growth, and reproductive rates are generally consistent with field observations. Improved predictions of E. pacifica dynamics have implications across a broad range of issues, including estimates of forage biomass and research focused on life history strategies and population dynamics. The enhanced IBM I have developed strengthens the foundation for such models to serve as tools for broader examination of dynamics within the California Current Ecosystem.

Citation Style