Management of Hybrid Watermilfoil (Myriophyllum sibericum x spicatum) using Diver Assisted Suction Harvesting

Transcription

1 2527 Lake Ottawa Road Iron River, MI Management of Hybrid Watermilfoil (Myriophyllum sibericum x spicatum) using Diver Assisted Suction Harvesting Lake Ellwood, Florence, WI Final Reporting Date: Submitted To: Lake Ellwood Association Wisconsin Department of Natural Resources Submitted By: Many Waters, LLC 2527 Lake Ottawa Road Iron River, MI Contact: Bill Artwich: billartwich@gmail.com, Barb Gajewski: barb@manywatersconsulting.com, Lake Ellwood, Florence County, WI DASH 2014 Page 1

2 Introduction The Lake Ellwood Association solicited the services of Many Waters, LLC to utilize their Diver Assisted Suction Harvesting (DASH) program to manage for Hybrid watermilfoil (HWM) from Lake Ellwood, located east of Florence in Florence County, WI. DASH is a mechanical process and requires a mechanical harvesting permit (Form (R 3/04)) from the Wisconsin Department of Natural Resources (WDNR). In 2014, the Lake Ellwood Association submitted and received a Mechanical Harvesting Permit from the WDNR to utilize DASH (Permit ID # M-NOR , WBIC: ). Onterra, LLC determined DASH site selection and provided mapping information. Dive Methods While using DASH, a diver typically begins by locating a EWM plant from the surface, and then descends next to the plant while lowering the nozzle. Divers works along the bottom by using fin pivots, kneeling on the bottom or hovering above the bottom at a distance where the root mass of the plant is within hands reach. Due to very soft sediments in Lake Ellwood, the diver typically suspended off the bottom to minimize sediment disturbance that greatly affects diving visibility. Divers either feed the Diver Feeding EWM Plant into Suction Hose top of the plant into the hose first and then uproot the plant or uproot the plant and feed it root wad first into the hose. It is very important that the diver shake as much sediment from the root wad before getting the root wad near the nozzle. Shaking the root wad away from the nozzle helps maintain visibility for the diver and minimizes debris and sediment in the holding bins. Plants fed into the nozzle are carefully observed for fragmentation. If fragmenting does occurs, the diver will catch floating fragments and feed them into the nozzle. Work sites that have dense monotypic beds, as in the case for Lake Ellwood, the initial DASH efforts are quite simple. The diver will descend adjacent to the bed and begin hand pulling or harvesting systematically across the bed to dismantle the bed. Once the bed is dismantled, a more systematic approach follows to target remaining clustered, scattered or outlier plants in the work site. As part of our method for covering a work area while using DASH (or divers alone), a grid pattern is used. A diver will start at either the port or starboard side of the boat and work to and from the boat perpendicular to the direction the boat is facing. For example, with the boat facing north and the diver starting on the port side, the diver begins by heading west. The diver will continue to work perpendicular to the boat until reaching the end of the suction hose. The diver then works back to the boat on a new transect line. Distance between each transect is dictated by visibility, density of plants, and obstructions. This process is repeated on the opposite side and in front of the boat. Depending on the site, once the diver has adequately covered the area which the suction hose can reach, the diver will signal the deckhand to let out more anchor line or determine that the boat needs re-positioning. Lake Ellwood, Florence County, WI DASH 2014 Page 2

3 Once plants reach the surface, a hose dispenses the plant material into a series of screened bins located on the deck of the boat. These bins capture plants and allow water to drain out back into the lake. Plants on deck are sorted into two categories: the targeted invasive plant and incidentally harvested native vegetation. Two wet weights are taken, one weight of the invasive plant and one weight for all native species combined. All plants are placed in sealable containers or bags for transport to the dumping site. The dumping site is a pre-determined site upland, away from any water body. Figure 1: 2014 DASH Work Areas (Onterra, 2013) Lake Ellwood, Florence County, WI DASH 2014 Page 3

4 Figure 2: 2014 Amended DASH Work Areas (Onterra, 2014) Lake Ellwood, Florence County, WI DASH 2014 Page 4

5 Results and Summary Table 1: Summary of DASH efforts Date Location Size 2013 (acres) Size 2014 (acres) Ave. Depth (ft) DASH Boat Location Lat (NAD 83) Long (NAD 83) Dive Time (hrs) Native (lbs*) Incidnetial Non-Target Harvest (lbs*) Total (lbs*) 7/7/2014 C % /7/2014 B % /9/2014 E <1% /10/2014 E <1% /10/2014 F <1% /11/2014 F % /11/2014 C % /14/2014 D % /8/2014 I-14 ** % /12/2014 A % /12/2014 I-14 ** % /13/2014 A <1% /13/2014 G-14 ** <1% ~1% *wet weight **Found in 2014 Table 2: Wet weight of HWM removed per site Site HWM Pounds A B C D E F G I HWM (lbs*) Lake Ellwood, Florence County, WI DASH 2014 Page 5

6 DASH efforts were set to comence on June 23 rd 2014, however upon arrival a early season algal bloom considerably hindered visibiltiy, postponing DASH efforts until conditions improved. Algal Bloom on Lake Ellwood June 23 rd 2014 July 7 th 2014 Weather - 75 F, sunny, NNE winds mph Algal bloom still present, however water clarity improved providing adequate diving visibility. DASH efforts initiated at the northeast corner of C-14. The harvester positioned adjacent to the work site facing southsouthwest. Three quarters of one dive hour harvested 29 pounds of HWM. The harvester repositioned at the southern end of B-14 and continued to work facing north. Two and a half hours at B-14 harvested 298 pounds of HWM. July 9 th 2014 Weather - 72 F, sunny, north wind 5-10 mph DASH efforts focused on E-14. The harvester positioned along the northeastern portion and worked north, east and west. Five and a quarter dive hours removed 707 pounds of HWM. Non-target incidental harvest of aquatic native plant species consisted of N. flexilis, P. richarsonii, P. illinoesis and S. pectinatus. Lake Ellwood, Florence County, WI DASH 2014 Page 6

7 July 10th 2014 Weather - 75 F, partly cloudy, SSW wind < 5mph DASH efforts began at E-14. The harvester anchored along the southwestern portion and worked facing south. Two and one quarter hours of dive time removed 163 pounds of HWM at E-14. Harvesting efforts continued at F-14 along the southwest end. Working facing northeast, one and three quarter dive hours removed pounds of HWM at F-14. Non-target incidental harvest of aquatic native plant species consisted of N. flexilis, P. richarsonii and V. americana. July 11 th 2014 Weather - 70 F, overcast, calm winds Returning to F-14, the harvester positioned along the west central edge and worked facing east. One and three quarter dive hours removed 190 pounds of HWM. Repositioning centrally at C-14, 1.75 dive hours removed an additional 190 pounds of HWM. July 14 th 2014 Weather - 57 F, cloudy, light winds, rain DASH efforts focused on D-14. Working the southern half of D-14, 3.75 hours of dive time removed pounds of HWM. Heavy rain ceased efforts. Non-target incidental harvest of aquatic native plant species consisted of N. flexilis, P. richarsonii and S. pectinatus. August 8 th 2014 Weather - 75 F, sunny, calm winds The harvester positioned northwest of I-14 and worked facing south. Five and one quarter hour of harvesting removed pounds of HWM. August 12 th 2014 Weather - 53 F, heavy overcast, NNW winds mph gusts to 20 mph Harvesting efforts focused on A-14. The harvester positioned along the southwestern edge and worked facing north-northeast. Four and a half hours of dive time removed pounds of HWM at A-14. Repositioning at I-14, along the eastern work edge facing west, 1.25 hours of dive time removed an additional 147 pounds of HWM. August 13 th 2014 Weather - 65 F, mostly sunny, winds N mph The Harvester returned to A-14. Positioned east of the work area working west, one hour of dive time removed 80.5 pounds of HWM. Repositioning south of G-14, working north, 4 hours of dive time removed an additional 466 pounds of HWM. Lake Ellwood, Florence County, WI DASH 2014 Page 7