Colin Pillai

A variety of invasive fishes including bigheaded carp are now advancing up the Mississippi River through its locks and dams, threatening to damage ecosystems in Minnesota. If aversive cues that deter carp could be identified and added to these locks and dams, the invasion might be stopped. One possibility would be to create a “curtain” of gas, perhaps containing loud sound, that could be placed into locks. As a first step, my project tested the possibility a carbon dioxide-infused bubble curtain could be used in such a manner. I used rainbow trout as a model species because they are: easy to procure, do well in a laboratory setting, and their nervous systems are already known to detect low concentrations of CO2. Rainbow trout were placed into a custom-built laminar flow tank while either: nothing was added to it (control), using an aquarium bubbler compressed air was added across its midline, or CO2 added via the same method. Fish crossing the air/CO2 stream was noted, as was their location either upstream or downstream of the midline for 30 minutes. An ANOVA was used to compare passage and distribution data. We found that while air had no measurable effect on passage (-2% decrease) and some effects on time spent downstream ( -43% P<0.05), CO2 had large effects, reducing passage by almost 63% (P<0.05) and the time spent downstream by 84% (P<0.05). With this data we can conclude that CO2 does affect the passage of rainbow trout, deterring them from crossing a bubble-curtain.