An ensonified bubble curtain blocks 4 species of invasive carp in a laboratory flume but also deters other fish, while sound alone is less effective overall and does not target carp

Abstract

Four species of invasive carp from Asia are advancing up the Mississippi River through its locks and dams (LDs) and threatening to profoundly alter its ecosystems. It has been hypothesized that sensory stimuli could be projected into locks to block carp movement through LDs. Sound has garnered special attention because carp are members of Ostariophysi, a group of fish with an exceptional sense of hearing. Further, it has been found that a broadband cyclic sound is especially effective at blocking bighead and common carp and that when projected into an air curtain to create an ensonified bubble curtain (EBC), blockage rates for these species exceed 90%. However, whether an EBC might especially effective at blocking all carps, and what its effects might be on native non-ostariphysians and why, has not been addressed. To answer these questions, this study examined the responses of 10 fishes including 4 invasive carps (common, bighead, silver, grass), 2 native Ostariophysi (channel catfish, golden shiners), and 4 native non-ostariophysians (rainbow trout, largemouth bass, bluegill sunfish, lake sturgeon) in a darkened laboratory flume while either a cyclic sound was played on its own, or projected into an air curtain. The EBC blocked all 4 carps 92-97% of the time without habituation, but 5 native fish were also partially blocked. In contrast, sound alone only blocked 2 carps and affected the other fishes to varying extents. An EBC appears uniquely well-suited to blocking carp invasions if native fish movement is a secondary concern.