Consultant's Report - Minnesota State Legislature

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Lake Ossawinnamakee and Pelican Brook - Zebra mussel occurrences Summary of some DNR surveys Response to FishPro information question I - Current Zebra Mussel Populations Gary Montz, Division ofEcological Services, MN-DNR 31 Jan 2005 Lake Ossawinnamakee zebra mussel sampling 2003: Zebra mussels were reported to the Area Fisheries Manager in Brainerd in late fall on a dock removed from the lake by a commercial dock hauler. Specimens were confitmed in the Aquatic Invertebrate Biology office in St. Paul. A single day survey was done ofvarious random shoreline sites. Survey methods involved wading in the shallow water, picking up rocks and woody debris at random, and examining for zebra mussels. Attached zebra mussels were found in several sites in the east-west main portion ofthe lake. Numbers were very low, less than 5 on any object, often only 1 - 3. Most were smaller size (approximately 1/4 - 3/8" long) suggesting settlement from 2003 reproductive effort. A few larger (314+" long) specimens were found, documenting the presence ofreproductive size, +1 year old mussels. Submerged rooted aquatic vegetation was randomly sampling by casting a plant hook out and pulling it back along the bottom. Zebra mussels were more common on a few sites attached to aquatic vegetation, generally on the main stem area. Vegetation collected from as deep as 16+' had attached zebra mussels. Zebra mussels were not found at a shoreline survey site on the northern arm ofthe lake, approximately % ofthe way up this portion ofthe lake. 2004: Early spring (May) shoreline sampling again documented zebra'mussels on woody debris, rocks and on submerged aquatic vegetation. Very few were found in shallow water. However, in surveys on Lake Zumbro (a zebra mussel infested lake in southern MN on the Zumbro River) it has been found that mussels are not found in spring in shallow zones corresponding to ice-zones in the lake, suggesting that winter ice cover kills and scours mussels attached in these shallow zones. Veliger sampling (data in separate file) detected veligers in mid-June, documenting successful reproduction. Dive surveys were done in August in the lake. In the east-west basin, a site was chosen that was towards the western end ofthe lake. The lake bottom rises up to within about 10' of the surface and the substrate is sand, sand/silt, rocks and cobble and submerged aquatic vegetation. Zebra mussels were common in this area, from the top ofthe rise to a depth ofapproximately 20', where the rocks become less common and the thermocline was well established. Mussels were found in varying numbers, ranging from 5 - 20+ on an individual rock. Multiple size classes were present, varying from the current years settlement to larger multiple year age adults. Mussels could be easily found over a large area oflake bottom. A second site was chosen on the northern arm ofthe lake, about % ofthe way north. At this site no zebra mussels were collected in survey. A third dive was done near the outlet ofKimball Creek (a small creek connecting Kimball Lake with Lake Ossawinnamakee, flowing into Ossawinnamakee). Substrate here was silt, with abundant submerged aquatic vegetation. No zebra mussels were documented in this area. General conditions: Mussels observed and collected were attached to various substrate (natural as well as man-made) and appeared healthy. Presence oflarger size mussels indicates survival ofzebra mussels in the waters ofthe lake. Collection ofveligers and occurrence ofsmall zebra mussels (new settlement) indicates that reproduction has
occurred successfully. Examination ofunpreserved water sample collected in plankton net tow documented living veligers, evidenced by cilia movement and action. Pelican Brook zebra mussel sampling 2003: Spot surveys ofthe brook immediately below the water control structure documented single or few attached zebra mussels sporadically attached to rocks and large woody debris. Further wading surveys by area fisheries and Exotic Species Program biologists during the fall found scattered sporadic attached zebra mussels up to 0.5+ miles downstream. Spot surveys at the next road crossing (approximately 2.5 miles downstream from the water control structure) found no attached zebra mussels. 2004: Spring spot surveys confirmed a similar finding as in fall 2003, with sporadic scattered attached zebra mussels found in the vicinity ofthe water control structure. As in 2003, no zebra mussels were documented at the next road crossing over Pelican Brook. Sampling in fall (after end ofweekly copper sulfate treatments to Muslde Bay, immediately adjacent to Pelican Brook) found no attached zebra mussels in the outlet area, and none downstream. It is suspected that the maintenance ofcopper sulfate, through the bay treatment, led to the elimination ofthe attached zebra mussels. Source ofinitial infestation ofLake Ossawinnamakee: The initial source for zebra mussels is unknown and likely will remain unknown. Zebra mussels are found in some <strong>Minnesota</strong> waters (Duluth/Superior Harbor, Mississippi River, Lake Zumbro) as well as in a number oflakes in states to the east (approximately 50 in Wisconsin, 200+ in Michigan). Zebra mussels can attach to boats or any other equipment left in infested waters, as well as aquatic vegetation and other natural substrates. Thus, it is impossible to document how the mussels entered the lake. However, veliger sampling and settled juveniles suggest that there are sufficient adults to sustain the population at this time.
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List ofTables MINNESOTA DEPARTMENT
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I. Introduction Purpose MINNESOTA D
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Feasibility Study To Limit the Spre
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Hydrological Characteristics MINNES
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Outlet Structure MINNESOTA DEPARTME
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lBhsl Nllrtq Osso'winnomakee Pelica
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Age and Growth MINNESOTA DEPARTMENT
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Works Cited MINNESOTA DEPARTMENT OF
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Table V-1. Methods Available for Co
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Cavitation MINNESOTA DEPARTMENT OF
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Potassium Salts MINNESOTA DEPARTMEN
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Works Cited MINNESOTA DEPARTMENT OF
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Combined Treatments MINNESOTA DEPAR
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Feasibility Study To Limit the Spre
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METHOD OF INVESTIGATION MINNESOTA D
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VII-B. Treatment Alternatives Expan
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Message Page 3 of4 3/21/2005 best.
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enougl1 to eV8Juatc £1'
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I \ I iV!1';UJIOOiS for Estimaling
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FishPro Consulting Engineers and Sc
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./}' 03/16/2005 14:40 FAX 217585189
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Page 192: VII-H. Glossary of Terms
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Consultant's Report - Minnesota State Legislature

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