Correspondence
Gaute Kjærstad, Department of Natural History, NTNU University Museum,
Norwegian University of Science and Technology, Trondheim, Norway.
Email: gaute.kjarstad@ntnu.no
Acknowledgements
We thank the Norwegian Environment Agency and the County Governor of
Nordland for financial support. We are grateful to Mark Daverdin, Lars
Rønning and Aslak D. Sjursen for assisting the field work. Antti P.
Eloranta gave valuable comments on an earlier draft of the manuscript.
Abstract
Biological invasions are regarded as one of the largest threats to
native biodiversity. The eradication of non-native parasites by culling
of hosts are a controversial conservation strategy, particularly when
using indiscriminate methods involving whole ecosystem collateral
damage. While short-term effects are abundantly documented, long-term
surveys are needed to detect potential wider ecosystem effects.
Here, we report a six-year study on effects of the piscicide rotenone on
invertebrate communities from a Norwegian water course using a
Before-After-Control-Impact design. Kick-net samples of benthic
invertebrates were collected from three lentic sampling stations and two
lotic stations two to four times per year in both a control and a
treated watershed.
In general, only relatively minor short-term effects immediately after
the treatment on species turnover, measured as temporal beta-diversity,
of benthic invertebrates were observed both in lentic and lotic
locations. However, the lotic fauna was temporarily severely negatively
affected following a period of rotenone exposure from an upstream lake.
Species turnover co-varied markedly between control and treatment
locations, indicating that natural environmental variation override
effects of rotenone treatment. Likewise, the abundance of invertebrate
taxa varied considerably both over time and between control and
treatment locations.
Our study indicates minor short-term (i.e. < one month) or
long-term (i.e. four years) effects of rotenone treatment on benthic
invertebrates, but severe effects on the lotic fauna eight months after
treatment. However, long-term effects are likely to be taxa-specific and
vary depending on habitat connectivity and thus potential for
re-colonization and will differ among locations and among taxa.