In 2019, the Norwegian Food Safety Authority decided to close the fish ladder in Hellefossen. This was done to exclude the stretch upstream of Hellefossen in a future treatment of the river to get rid of Gyrodactylus salaris. Provided that Hellefossen functions as an absolute barrier to fish migration, the area upstream will over time become free of Atlantic salmon and G. salaris.

To document if the closure of the fish ladder in Hellefossen has had the desired effect on reducing the Atlantic salmon and G. salaris population, the Norwegian Food Safety Authority, NFSA, commissioned the Norwegian Veterinary Institute, NVI, to carry out surveillance in River Drammenselva, starting from 2020. In 2022, NFSA further commissioned NVI to carry out surveillance for G. salaris in lakes draining into the River Drammenselva catchment upstream of the anadromous part of the river.