Effects of Rotenone Treatment on Lotic Invertebrates

Abstract

Two rivers in Norway were treated with rotenone in an effort to eradicate the salmon parasite, Gyrodactylus salaris. Rotenone induced an immediate catastrophic invertebrate drift, mainly of dead individuals. The response to rotenone with respect to degree and timing varied widely. Baetis rhodani, Isoperla sp. and Rhyacophila nubila displayed a strong increase in drift densities early in the treatment. Baetis niger, Ameletus inopinatus, Heptagenia sp. and Agapetus ochripes showed a delayed response. Ephemerella aurivillii, E. mucronata, Taeniopteryx nebulosa and Elmis aenea drifted at low densities throughout the treatment. Early larval instar tended to be more sensitive to rotenone than later instar, and the toxic effect of rotenone tended to increase with increasing water temperature.Different taxa were exposed to rotenone under similar conditions during in situ aquarium experiments. Despite different habitat preferences, which could lead to different exposure to rotenone, the response-patterns in the in situ aquarium experiments for the particular taxa was similar to those observed in the drift samples.

Effects of Three Consecutive Rotenone Treatments on the Benthic Macroinvertebrate Fauna of the River Ogna, Central Norway

“…suphurea . Ameletus has shown to be rotenone sensitive (Gladsø and Raddum, ) and Heptageniidae to have an intermediate tolerance (Engstrom‐Heg et al ., ; Kjærstad and Arnekleiv, ). Even the relative rotenone tolerant Ephemerella (Engstrom‐Heg et al ., ) had a marked density decrease after the third treatment.…”

“…had reduced densities at the treated station after all three treatments, while the densities at the untreated station had a slight increase during the same time period. Rhyacophila is known to be rotenone sensitive (Engstrom‐Heg et al ., ; Arnekleiv et al ., ; Gladsø and Raddum, ), and Agapetus ochripes has been cited with an intermediate rotenone tolerance (Kjærstad and Arnekleiv, ). During the third treatment all Trichoptera taxa showed decreased densities at the treated station, but all were present immediately after the treatment, but in low densities.…”

“…rhodani and B . muticus has been documented, the former being the most sensitive (Kjærstad and Arnekleiv, ). Other mayfly species which seemed to be negatively affected by the treatments included Ameletus inopinatus , Heptagenia dalecarlica and H .…”

“…Taxa from the orders Ephemeroptera, Plecoptera and Trichoptera (EPT) are particularly sensitive, although some species within these orders are tolerant (Mangum and Madrigal, 1999;Arnekleiv et al, 2001). Some studies report tolerance differences in larval stages, with early stages more sensitive than later stages (Gladsø and Raddum, 2002;Kjaerstad and Arnekleiv, 2011). Recovery time of invertebrate densities after rotenone treatments varies, but has been registered as fast as within a year (Binns, 1967;Kjaerstad and Arnekleiv, 2004).…”

Why Should We Preserve Fishless High Mountain Lakes?

“…However, their use has ecological effects on native fauna such as invertebrates (e.g. Dalu et al 2015;Kjaerstad and Arnekleiv 2011), and legal and social complications, especially in protected areas because the very notion of a protected area implies that it remains chemical free. It is important to highlight that eradication actions are a "second step", which should come when protection measures (fishing ban and the prohibition of fish stocking) are already in place and effectively enforced; if these fundamental guarantees are absent or weak, the local context (i.e.…”