Rotenone is a compound used to rid streams of the salmon parasite Gyrodactylus salaris. But it is not always easy to know how much rotenone should be used to treat a river effectively, and how much the substance will spread. Too much rotenone is both expensive and environmentally harmful, while too little allows the parasite to survive. The entire Vefsna watercourse must now be treated with rotenone. In this context, the Norwegian Veterinary Institute and NTNU are working together to simulate rotenone treatment by using harmless fluorescent dyes.
After the dye is released, the researchers can then accurately measure how the substance spreads and how quickly. Thus, the location, amount and timing of rotenone treatment can be planned and customized to the river. The idea of simulation using dyes to trace the movement of substances is not new, but this is the first time this information has been combined with a data series that provides comprehensive information for an entire river system.