Rotenone for exotic trout eradication: nontarget impacts on aquatic communities in a mountain lake

Abstract

Beaulieu J, Trépanier-Leroux D, Fischer JM, Olson MH, Thibodeau S, Humphries S, Fraser DJ, Derry AM. 2021. Rotenone for exotic trout eradication: nontarget impacts on aquatic communities in a mountain lake. Lake Reserv Manage. 37:323–338.

Rotenone is widely used in lake and reservoir management for the eradication of exotic fish. However, nontarget effects of rotenone on freshwater organisms such as zooplankton and macroinvertebrates are of concern because of the ecological importance of these organisms in aquatic food webs as a resource base for fish, especially when rotenone is applied to lakes prior to native fish reintroduction. The objective of our study was to determine the effects of rotenone on nontarget zooplankton and macroinvertebrate species assemblages in a headwater mountain lake where rotenone was applied to remove exotic brook trout (Salvelinus fontinalis; Banff, AB Canada). We found strong negative rotenone impacts on the community structure and density of crustacean zooplankton, and to a lesser extent on macroinvertebrates, lasting for at least 1 yr after the rotenone treatment. Our study offers 2 unique insights that differentiate from rotenone studies on other lakes: (1) the persistent and almost complete eradication of crustacean zooplankton in the following summers, 11 months after rotenone treatment, and (2) a considerable shift in the macroinvertebrate community composition, likely resulting from combined effects of both nontarget rotenone effects on taxon density and trophic interactions associated with the eradication of brook trout from the lake. We advocate that assisted recolonization in the restoration of aquatic food webs could play an important role in facilitating nontarget aquatic community recovery following lake rotenone treatment.

Keywords:

• Aquatic community reestablishment
• exotic fish removal
• mountain lake
• nontarget impacts
• rotenone

Acknowledgments

We thank M. Daneau-Lamoureux, M. Lagacé, M. Salamon, L. Astorg, M. Yates, A. Yaghi, and S. Urschel for their field assistance and M. Daneau-Lamoureux, Marion Thellier, and Léa Fillon for laboratory assistance. We thank the Parks Canada Agency for permission to conduct research in the National Mountain Parks of Canada.

Data Availability

The data are available in the repository of the Environmental Data Initiative (EDI).Zooplankton: https://doi.org/10.6073/pasta/b27053aaabbff61248819a7396b9dad2Macroinvertebrates: https://doi.org/10.6073/pasta/3bc27eeccd0f943fe7d19678bd67a6ad

Additional information

Funding

This research was supported by funding from a Natural Sciences and Engineering Research Council of Canada (NSERC) Strategic Project grant (AMD, DJF), a Fonds de Recherche Nature et technologies Québec team grant (AMD, DJF), and a grant from the National Science Foundation (NSF DEB-1754181; JMF, MHO). Students were supported by the following funding sources: Groupe de recherche en limnologie Québec (GRIL) to JB and DT-L and a NSERC-USRA award to ST.