DEEP WATER MECHANICAL HARVESTING OF HYDRILLA IN WEST LAKE TOHOPEKALIGA, FLORIDA

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1 DEEP WATER MECHANICAL HARVESTING OF HYDRILLA IN WEST LAKE TOHOPEKALIGA, FLORIDA Dean Jones 1, 2, William Haller 2 and Mike Hulon 3 1 Osceola County 2 University of Florida 3 Texas Aquatic Harvesting, Inc.

2 Demonstration Project on Hydrilla and Hygrophila Osceola County awarded $2.8 million by the EPA for this project Goal: To find new and alternative methods of control for hydrilla and hygrophila and to share the findings with the industry and public

3 Why Reconsider Harvesting? Little research on mechanical harvesting since 1970 s, Orange Lake, Florida Small harvesters Maximum cutting depth of 5 feet Visually see hydrilla (surface mats) Rapid re-growth High fish by-catch Most opinions about harvesting hydrilla are based on this work and data

4 Other Considerations Endangered species restrictions Everglades Snail Kite (Rostrhamus sociabilis) Limited management resources Herbicide resistance and costs Integrated Pest Management Equipment and technology advances Compare results with Orange Lake Study Haller et al Fish by catch data Observation hydrilla did not return in some areas harvested for approximately one year

5 Aquamarine H-650

6 Aquamarine Aquatrio

7 Aquamarine Aquatrio

8 Orange Lake Study

9 Model 800 Mechanical Harvester

10 Equipment Advances

11 Technology Advances

12 Goals Harvest a 40 ha area (100 acres) of deep water hydrilla in West Lake Toho Determine Efficacy and longevity of control Is Deep Water Hydrilla Harvesting efficient? Can we harvest root crowns? Determine fish by catch and compare with Orange Lake Study results Is it possible to reduce fish by-catch? Determine magnitude and duration impacts of selected water quality parameters before, during and following the harvesting operation

13 Efficacy

14 Efficacy

15 1 DAT Comparison

16 2 MAT Comparison

17 Efficacy and Longevity Interval Date PAC PVI Pre-treatment 1/30/ DAT 3/19/ MAT 5/17/ MAT 6/19/

18 Fish By Catch Comparison

19 Fish By Catch Comparison

20 Fish By Catch Comparison

21 Harvester Performance Area (ha) (ac) Transect Number Area (ha/hr) (ac/hr) Weight (hydrilla) kg/trans. lbs/trans. kg/ha lbs/ac ,350 1, ,646 1, ,

22 Fish By Catch Fish Total Results Bluegill Redear Warmouth Black crappie No. WT(g) No. WT(g) No. WT(g) No. WT(g) Total Sportfish No. WT(g) Total All Fish* No. WT(g) % sport fish No. WT(g)

23 Fish By Catch Comparison Fish Mean ± SD LAKE TOHO 2012 Total All Fish Harvested No./ha g/ha 299 ± 151 1,470 ± 712 ORANGE LAKE 1977 Total All Fish No./ha g/ha 66,000 ± 2,000 85,000 ± 12,000

24 Water Quality Impacts

25 Water Quality Impacts Water samples collected -7, -1, 0, 1, 4, 7, 15 days after harvesting 3 samples sites in harvest area 5 reference sites 1,000 m outside harvest area Water samples collected at depth of 1m Average depth of water samples sites is 2m

26 Results (harvest area and control) Secchi Higher in harvest plot 1 week before harvesting Total Chlorophyll Lower in harvest area 1 week before harvesting Total Nitrogen Lower in harvest plot 1 week before harvesting Total Phosphorus Lower in harvest area 1 week and 1 day before harvesting and 7 DAH Only post harvest statistical difference is phosphorus 7 DAT

27 Results (harvest area and control) Also no statistical differences observed in Turbidity Dissolved Oxygen ph Conductivity Temperature difference 1 and 4 DAT (result of time of day sampled)

28 Dissolved OXYGEN (mg/l) Depth (ft) Reference site Harvest site Surf Time of 1 st sample C Surface C Bottom

29 Dissolved Oxygen on 6/14/12 Site Time Depth DO (mg/l) Toho YSI 1 - Dense hydrilla 6:10 AM Toho YSI 3 - Dense hydrilla 6:55 AM

30 Comparison Summary Parameter Orange Lake Lake Tohopekaliga Cutting depth 5 feet 10 feet Hydrilla biomass harvested 12 tons per acres < 1 ton per acre Hydrilla distribution 80% top 2 feet 100% bottom 4 feet Dissolved oxygen Low in bottom ½ of water column Uniform throughout water column By catch 66,000 fish per ha 299 fish per ha Length of control 2-4 months > 4 months Acres per hour harvested <1 2.2

31 Conclusions Deep water harvesting of hydrilla is a potentially feasible method of control Equipment/technology advances combined with the growth stage of hydrilla allow for a more efficient and cost effective harvesting operation Limnological conditions, time of year and growth stage of hydrilla determines fish by-catch Preliminary water quality data suggests minimal impacts Data supports additional R&D and evaluations

32 Acknowledgements Osceola County Board of County Commission United States Environmental Protection Agency Texas Aquatic Harvesting Inc. Florida Fish and Wildlife Conservation Commission South Florida Water Management District Analytical Services Lab