Water Flow Sensing and Orientation Describing Fish Navigation, Guidance, and Passage Near Infrastructure Across a $40M Data Set

In an era of austerity, environmental mitigation as it relates to infrastructure will likely have to contend with far fewer design iterations in order to successfully compete for limited budgetary resources. To improve knowledge of fish behavior with the goal of reducing future design iterations, I analyzed the movement behavior of fish across a large data set (47 scenarios, 14 years, 7 dams) when water flow was concurrently measured. Results support observations dating back to the 1950s, and earlier, regarding the importance of water acceleration and inertial stimuli in fish movement. Further, I developed a hypothesis for how water acceleration “shapes” individual movement trajectories. Findings support the notion that fish, like other animals, evaluate the world in relative terms. Key to this concept is how a fish updates its baseline reference, against which it compares instantaneous experiences (just noticeable difference). While I represent the shifting baseline using an acclimatization function, I suggest the shift may stem more from a change in risk disposition or other process capable of modifying the subjective valuation of acceleratory stimuli. Effort is underway to improve the realism of the assumed process(es) that underlie why fish change their response to unchanging water flow pattern.