Since the 1970s, several species of Asian carp have advanced northwards through the watersheds of the Midwestern US, feeding voraciously and proliferating freely in the absence of natural predators. Today they threaten the Great Lakes, where scientists alongside the US Army Corps of Engineers have undertaken several projects to deter invasive carp from establishing a foothold.
Cory Suski and researchers at the University of Illinois (Urbana-Champaign) have now demonstrated the potential of a new tool in this endeavor. In laboratory experiments, Suski's team exposed mature and juvenile silver carp and bighead carp (and two other species) to different levels of hypercarbia. They then assessed mRNA expression and movement to determine how carbon dioxide elicits stress and avoidance behavior in each species (Biol. Invasions 17, 3133–3151; 2015). The results were encouraging. “Juvenile fishes of all four species actively avoid areas of water with elevated CO2 once concentrations reached approximately 200 milligrams per liter, which is lower than a can of carbonated soda,” summarized Suski in a press release. Carbon dioxide is also relatively cheap and safe, compared to other barrier techniques, so it is a promising candidate for new and supplemental barriers to deter invasive fish. GDL
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