The impacts of exotic species on native fish

The impacts of exotic species on native fish assemblages By: Heather Bradley, James Hulslander & Katie Mc. Gohan Photo by: Heather Bradley

Sources of exotic species to lakes ¡ Accidental l ¡ Ballast water Bait bucket dumping Aquaria Intentional l l 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 l ¡ 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! l l l 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 l l 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: ¡ l l 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? ? ?