impacts of invasive spiny water flea (bythotrephes cederströmii) on walleye (sander vitreus) mercury accumulation, ecosystem biomagnification, and bioenergetics
abstract
an evolving threat to freshwater ecosystems is invasive species. the spiny water flea
(bythotrephes) is an invasive zooplankter well known for its severe negative impacts on
native freshwater zooplankton, but some knowledge gaps exist regarding their impacts to
fishes, high-level trophic organisms, and food chains. changes in trophic positions at all
levels of the ecosystem can affect contaminant concentrations in large organisms. in this
study i used walleye (sander vitreus) total muscle mercury concentration ([mehg]) and
size data, as well as stable isotope ratios and a bioenergetics model to evaluate the
potential impacts of bythotrephes on the build up of toxic metals in fishes. i expected to
see an increase in walleye mercury concentration and a systematic impact of
bythotrephes on walleye growth efficiency. in my first data chapter (chapter 2) i found
that the presence of bythotrephes was associated with an increase in small (<50cm)
walleye [mehg] in quetico provincial park and in rainy lake. these results suggest that
bythotrephes have a greater impact on hg accumulation in smaller fish and may alter
walleye growth trajectories. [...]