The impacts of exotic species on native fish assemblages
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The impacts of exotic species on native fish assemblages. By: Heather Bradley, James Hulslander & Katie McGohan. Photo by: Heather Bradley. Sources of exotic species to lakes. Accidental Ballast water Bait bucket dumping Aquaria Intentional Game fish stocking

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The impacts of exotic species on native fish assemblages

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The impacts of exotic species on native fish assemblages

By:

Heather Bradley, James Hulslander & Katie McGohan

Photo by: Heather Bradley


Sources of exotic species to lakes

  • Accidental

    • Ballast water

    • Bait bucket dumping

    • Aquaria

  • Intentional

    • Game fish stocking

    • Unofficial stocking by locals


Research Questions

  • Does the number of native fish species in a lake decrease as the number of exotic fish species increases?

  • What impact do exotic species have on overall biodiversity within the lake?

  • Which habitats support more diverse fish communities?


Why ask these questions?

  • Large predatory fish stocking

    • Native fish are likely to be out competed or consumed by these predators

  • Exotics may not have natural predators in the new system they are introduced to


How to answer these questions?

  • Go Fishing!

    • Trap nets, Gill nets and minnow traps

    • Cover as many habitat types within the lake as possible

    • Catch LOTS of fish (and their delightful parasites)


Methods continued….

  • Sample the invertebrates of the lake

    • Important for assessing food availability and making comparisons between lakes

    • Plankton tows, Ekman grab samples


Diversity by Lake


Diversity by Lake and Habitat


Diversity Results

  • Wolf Lake highest richness

  • Wolf Lake highest Shannon Diversity (eveness considered)

  • Cranberry highest Simpson’s


Catlin Lake Biomass


Cranberry Lake Biomass


Conclusions

  • Exotic species impact fish species diversity

  • Wolf lake highest richness and diversity when evenness included

  • Biomass for native vs exotic species even for Catlin and Cranberry

  • 3 habitats vary in diversity but vegetated highest richness


Suggestions

  • Other sampling techniques for larger fish (gillnets, deeper water sets, rods)

  • More Samples collected in:

    • Varying weather

    • Huntington lakes

    • Seasons

    • More habitats


Sources of Error

  • Incorrect ID

  • Digital scales not working properly

  • Dead/mangled/rotting samples

  • More sampling of Cranberry

  • Net holes and mistakes


Treatment

  • Education of public

  • Biological Control?

  • Chemical treatments


Questions???


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