Short-Term Effects on Riverine Ephemeroptera, Plecoptera, and Trichoptera of Rotenone and Aluminum Sulfate Treatment to EradicateGyrodactylus salaris

Abstract

In Norway, attempts have been made to eradicate the salmon parasite Gyrodactylus salaris from infested rivers using solutions containing either rotenone or aqueous aluminum and sulfuric acid (AlS). When Steinkjewassdraget, a river system in central Norway, was being treated in summer 2007 with AlS and the rotenone formulation CFT Legumine, we investigated the immediate drift of Ephemeroptera, Plecoptera and Trichoptera in the River Wlla. The rotenone treatment induced catastrophic drift and caused mortality to the ephemeropterans Baetis fuscatus/scambus, Baetis muticus, Baetis niger, Baetis rhodani, Heptagenia dalecarlica, Heptagenia sp., and Ecdyonurus joernensis; to the plecopterans Amphinemura borealis, Amphinemura sp., Capniidae indet., Leuctra fusca, Leuctra sp., Nemoura avicularis, Perlodidae indet., Protonemura meyeri, and Taeniopteryx nebulosa; and, to the tichopterans Hydropsyche sp., Polycentropodidae indet., Polycentropusflavomaculatus, and Rhyacophila nubila. The AlS treatment induced catastrophic drift and had negative effects on the trichopteran Rhyacophila nubila, and the ephemeropterans B. rhodani, B. niger, and possibly B. fuscatus/scambus, although its effects on these species were less pronounced than those from the rotenone treatment. No effects on drift densities or mortalities were recorded for any of the plecopterans during the AlS treatment.

Fixed dose aluminum sulfate treatment to eradicate the salmon parasiteGyrodactylus salaris: effects on benthic macroinvertebrates

“…This is especially so in streams with low levels of dissolved organic carbon because humic substances may ameliorate some of the acidity effects by binding to metals (Raddum & Fjellheim 1984;Aanes & Baekken 1995). B. rhodani immediately increases activity when introduced to acid stress (Gerhardt 1990), starts drifting (Ormerod et al 1987;Raddum & Fjellheim 1987;Bongard 2005;Eriksen et al 2009), or dies (McCahon & Pascoe 1989Merrett et al 1991;Bongard 2005). Major reductions in populations of B. rhodani have also been found in relation to pH-regulated AlS doses (Halvorsen & Heergaard 2007).…”

“…This may ultimately lead to reduced breakdown efficiency of organic litter (Dangles et al 2004) and retarded ecosystem functioning (Pye et al 2012). Assays of macroinvertebrates in response to AlS treatments in rivers in Norway are few and show contradicting results À from minor to severe perturbation of population sizes of acid sensitive taxa (Bongard 2005;Halvorsen & Heergaard 2007;Kjaerstad & Arnekleiv 2007;Eriksen et al 2009). One explanation for this discrepancy could be that the AlS method has developed since its introduction both with respect to concentrations and composition of chemicals.…”

“…Slightly acidic water with pH in the range of 5.7À5.8 and low concentrations of inorganic monomeric Al (20À30 mg/L Al i ) may eradicate the parasite without having harmful effects on the salmon. However, acidity at this level may negatively affect acid sensitive macroinvertebrates (Halvorsen & Heergaard 2007;Eriksen et al 2009). These macroinvertebrates may be important prey for juvenile Atlantic salmon (Peterson & Martin-Robichaud 1986).…”

“…These macroinvertebrates may be important prey for juvenile Atlantic salmon (Peterson & Martin-Robichaud 1986). AlS treatments induce episodic acid stress by suddenly lowering pH and increasing concentrations of inorganic aluminum (Eriksen et al 2009;Hagen et al 2010). Similar acid episodes may regularly occur in acidified areas with base poor soils in association with heavy rainfall or snowmelt (Henriksen et al 1988;Lawrence 2002;Lepori et al 2003a).…”

“…G. salaris was introduced through the import of infested fish stocks during the 1970s and, so far, has been recorded in 45 Norwegian rivers (Johnsen & Jensen 1991;Jansen et al 2007). Recruitment of salmon has drastically declined in affected rivers and tremendous efforts have been made to eradicate the parasite from Norwegian rivers (Jansen et al 2007;Eriksen et al 2009). One…”