Eurasian Water-Milfoil Survey on Black Oak Lake (Vilas County, Wisconsin)

Submitted to:

Black Oak Lake Riparian Owners Association

Contact: John Annin

5817 North Black Oak Lake Road

Land O’ Lakes, Wisconsin 54540

Prepared by:

Contact: Dean Premo, Ph.D.

Fieldwork: David Tiller, B.S.

White Water Associates, Inc.

429 River Lane

Amasa, Michigan 49903

Phone: (906) 822-7889

Date: December 30, 2005

INTRODUCTION

In this document, we report the findings of a survey for Eurasian water-milfoil (Myriophyllum spicatum) in Black Oak Lake, Vilas County, Wisconsin. Eurasian water-milfoil is a non-native invasive species of aquatic plant. The species originated in Europe and Asia, but was introduced to North America many years ago and is now found over much of the United States. It reached Midwestern states between the 1950s and 1980s. It is spread between inland lakes primarily by boats. Eurasian water milfoil can become entangled in boat propellers, and may wrap around other external parts of the boat. Stems can become lodged among any watercraft apparatus or sports equipment that moves through the water, including boat trailers.

In nutrient-rich lakes Eurasian water milfoil can form thick underwater stands of tangled stems and vast mats of vegetation at the water's surface. In shallow areas the plant can interfere with water recreation such as boating, fishing, and swimming. The plant's floating canopy can also crowd out important native water plants.

A key factor in the plant's success is its ability to reproduce through stem fragmentation and underground runners. A single segment of stem and leaves can take root and form a new colony. Fragments clinging to boats and trailers can spread the plant from lake to lake. The mechanical clearing of weed beds for beaches, docks, and landings creates thousands of new stem fragments. Removing native vegetation creates perfect habitat for invading Eurasian water milfoil.

Eurasian water milfoil has difficulty becoming established in lakes with healthy populations of native plants. In some lakes the plant appears to coexist with native flora and has little impact on fish and other aquatic animals.

Black Oak Lake has been surveyed for aquatic plants in the past and Eurasian water milfoil has not been found. Nevertheless, concern exists among members of the Black Oak Lake Riparian Owners Association that Eurasian water milfoil has made contact with the lake through boaters. This concern prompted the survey that was conducted in fall of 2005 and reported herein.

STUDY AREA

Black Oak Lake is a 584 acre lake located near the town of Land O’Lakes in northern Vilas County, Wisconsin. It is a deep lake (>80 feet in places) and has a tremendous diversity of aquatic habitats (from shallow to deep water). Black Oak Lake can be best described as a “Groundwater Drainage Lake” even though it has a minor inflow of water from Dollar Lake to the north. Its outflow stream is small. There is a public park on the lake with a public swimming beach, picnic area, and boat landing. Black Oak Lake is an important resource used by the public for a diversity of recreational pursuits. Based on previous botanical work, Black Oak Lake has a diverse native plant community.

METHODS

David Tiller conducted the fieldwork for the Eurasian water-milfoil survey in October of 2005. The survey involved boating around the lake observing plant beds and collecting specimens to verify species.

RESULTS

We found no Eurasian water-milfoil in Black Oak Lake during the October 2005 survey. It is our opinion that Black Oak Lake habitat is not highly suitable for this species, but periodic surveys for this non-native plant species and others is a prudent approach to lake stewardship.