Transcript Group 1
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 Eveness Cranberry Wolf 0.2715 0.1648 1.6450 2.0588 16 19 0.5933 0.6992 Catlin 0.1682 1.9354 10 0.8405 Diversity by Lake and Habitat Lake Habitat Catlin Catlin Catlin Wolf Wolf Wolf Cranberry Cranberry Cranberry Vegetated Rocky Sandy Vegetated Rocky Sandy Vegetated Rocky Sandy Simpsons Shannon Richness Eveness 0.2966 0.2988 0.2879 0.2335 0.2455 0.2299 0.3278 0.2511 0.3093 1.5535 1.3350 1.3856 1.7597 1.7127 1.7854 1.2436 1.5074 1.4677 9 6 6 16 14 12 11 6 6 0.7070 0.7451 0.7733 0.6347 0.6490 0.7185 0.5186 0.8413 0.8191 Simpson's Diversity 0.3000 Diversity 0.2500 0.2000 0.1500 0.1000 0.0500 0.0000 Cranberry Wolf Lake Catlin Shannon Diversity 2.5000 Diversity 2.0000 1.5000 1.0000 0.5000 0.0000 Cranberry Wolf Lake Catlin Simpson's by Habitat 0.2500 0.2000 0.1500 0.1000 Vegetated Vegetated Rocky Rocky Rocky Sandy Sandy Sandy 0.0500 0.0000 Vegetated Simpson's 0.3500 0.3000 Catlin Wolf Cran Catlin Wolf Cran Catlin Wolf Cran Lake/Habitat Shannon by Habitat 1.5000 1.0000 0.5000 Rocky Sandy Vegetated Rocky Sandy Vegetated Rocky Sandy 0.0000 Vegetated Diversity 2.0000 Catlin Catlin Catlin Wolf Wolf Wolf Cran Cran Cran Lake/Habitat 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 44% native species exotic species 56% 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???