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

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

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

Simpson's Diversity

0.0000

0.0500

0.1000

0.1500

0.2000

0.2500

0.3000

Cranberry Wolf Catlin

Lake

Dive

rsity

Shannon Diversity

0.0000

0.5000

1.0000

1.5000

2.0000

2.5000

Cranberry Wolf Catlin

Lake

Dive

rsity

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

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

Diversity Results

Wolf Lake highest richness Wolf Lake highest Shannon Diversity

(eveness considered) Cranberry highest Simpson’s

Catlin Lake Biomass

Catlin Lake Biomass

49%

51%

49% native

51% exotic

Cranberry Lake Biomass

Cranberry Lake Biomass

56%

44%native species

exotic species

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???