An Engineering Perspective on Invasive Fish Control: A Study of Bubble Curtain Deterrent Systems to Control Carp Movement

Abstract

The objective of this research was to investigate the ability of bubble curtain deterrent systems to inhibit the movement of invasive fish. Bubble curtains, which consist of a wall of bubbles (e.g. produced by forcing air through perforated pipes), fall into the category of behavioral deterrent systems that rely on aversive stimuli (e.g. sound and light) to guide fish in taxon specific manners. These systems provide advantages over physical/mechanical screens because they do not restrict fluid flow or negatively impact navigation. Bubble curtains are particularly appealing, because they are less expensive than other electrical or sonic barriers, are easily maintained, safe, and produce complex acoustic and hydrodynamic stimuli which may be optimized to deter fish movement. However, few studies have examined whether or how bubble curtains might work. In three studies, the common carp (<italic>Cyprinus carpio</italic>), a cyprinid responsible for water quality degradation in shallow water ecosystems, was used to investigate how bubble curtains influence fish behavior and might be optimized. First, through a laboratory experiment, two different bubble curtains were shown to reduce passage of common carp by 75-80% in both up- and down-stream directions. These findings also suggested that avoidance behaviors were attributed to fluid motion and sound stimuli. Second, a field test demonstrated that the performance of a bubble curtain under natural conditions was consistent with laboratory results, blocking 57±12% of downstream swimming carp, versus 75-80% in the laboratory. Third, a fish movement model based on diffusion theory and phonotaxic response was derived. In a novel application, a stability analysis of the fish movement model demonstrated that acoustic stimuli produced by the bubble curtains can be sufficient to disrupt movement (i.e. deter passage) of common carp. Overall, I have shown through rigorous experimental and holistic quantitative analysis that bubble curtains can indeed deter common carp movement, but improvements must be identified in order for bubble curtains to remain a viable management tool in the future.