Simulating Movement Patterns of Blueback Herring in a Stratified Southern Impoundment

Abstract

J. Strom Thurmond Lake (Georgia-South Carolina) strongly stratifies during the summer, producing a temperature-dissolved oxygen “squeeze” for landlocked blueback herring Alosa aestivalis. A coupled Eulerian-Lagrangian hybrid (CEL hybrid) model was developed to improve understanding of and better predict the in-reservoir movements of blueback herring in response to these limiting conditions. An existing application of CE-QUAL-W2, a two-dimensional, laterally averaged water quality and hydrodynamic model, was used to simulate the spatial and temporal dynamics of summer water temperature, dissolved oxygen, and hydraulics. The biological module was parameterized by using mobile hydroacoustic survey data supplemented with species composition data from gill-net surveys. The simulation accurately described the longitudinal (r2 = 0.67) and vertical (r2 = 0.93) distributions observed for blueback herring. The model results suggest that the longitudinal distribution of blueback herring in summer is best explained by a random term (57%) and horizontal water velocity (43%). The vertical distribution is best explained by the following variables (in order of their importance): water temperature (45%), a random term (44%), dissolved oxygen (6%), horizontal velocity (4%), and vertical velocity (1%). The integration of fish behavior into a flow and water quality modeling framework can be used to gain insight into the response of coolwater species to flow and water quality patterns. This insight can serve as a foundation for population and bioenergetics modeling or be used to improve the management of coolwater fish and their habitats in dynamic reservoir systems. We recommend that additional data be used to further test and refine the model.