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The impacts of exotic species on native fish assemblages
By:Heather Bradley, James
Hulslander & Katie McGohan
Photo by: Heather Bradley
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Sources of exotic species to lakes
Accidental Ballast water Bait bucket
dumping Aquaria
Intentional Game fish stocking Unofficial stocking
by locals
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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?
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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
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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)
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Methods continued….
Sample the invertebrates of the lake Important for assessing food availability
and making comparisons between lakes Plankton tows, Ekman grab samples
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Diversity by Lake
Lake Simpson's Shannon Richness EvenessCranberry 0.2715 1.6450 16 0.5933Wolf 0.1648 2.0588 19 0.6992Catlin 0.1682 1.9354 10 0.8405
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Diversity by Lake and Habitat
Lake Habitat Simpsons Shannon Richness EvenessCatlin Vegetated 0.2966 1.5535 9 0.7070Catlin Rocky 0.2988 1.3350 6 0.7451Catlin Sandy 0.2879 1.3856 6 0.7733Wolf Vegetated 0.2335 1.7597 16 0.6347Wolf Rocky 0.2455 1.7127 14 0.6490Wolf Sandy 0.2299 1.7854 12 0.7185Cranberry Vegetated 0.3278 1.2436 11 0.5186Cranberry Rocky 0.2511 1.5074 6 0.8413Cranberry Sandy 0.3093 1.4677 6 0.8191
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Simpson's Diversity
0.0000
0.0500
0.1000
0.1500
0.2000
0.2500
0.3000
Cranberry Wolf Catlin
Lake
Dive
rsity
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Shannon Diversity
0.0000
0.5000
1.0000
1.5000
2.0000
2.5000
Cranberry Wolf Catlin
Lake
Dive
rsity
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Simpson's by Habitat
0.00000.05000.10000.15000.20000.25000.30000.3500
Vege
tate
d
Vege
tate
d
Vege
tate
d
Roc
ky
Roc
ky
Roc
ky
Sand
y
Sand
y
Sand
y
Catlin Wolf Cran Catlin Wolf Cran Catlin Wolf Cran
Lake/Habitat
Sim
pson
's
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Shannon by Habitat
0.0000
0.5000
1.0000
1.5000
2.0000
Vege
tate
d
Roc
ky
Sand
y
Vege
tate
d
Roc
ky
Sand
y
Vege
tate
d
Roc
ky
Sand
y
Catlin Catlin Catlin Wolf Wolf Wolf Cran Cran Cran
Lake/Habitat
Dive
rsity
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Diversity Results
Wolf Lake highest richness Wolf Lake highest Shannon Diversity
(eveness considered) Cranberry highest Simpson’s
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Catlin Lake Biomass
Catlin Lake Biomass
49%
51%
49% native
51% exotic
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Cranberry Lake Biomass
Cranberry Lake Biomass
56%
44%native species
exotic species
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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
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Suggestions
Other sampling techniques for larger fish (gillnets, deeper water sets, rods)
More Samples collected in: Varying weather Huntington lakes Seasons More habitats
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Sources of Error
Incorrect ID Digital scales not working properly Dead/mangled/rotting samples More sampling of Cranberry Net holes and mistakes
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Treatment
Education of public Biological Control? Chemical treatments
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Questions???