OBJECTIVE

To determine the relationship of environmental factors that corresponding to observed invasive and indigenous crayfish habitat.

DESCRIPTION

Background

The Wisconsin Department of Natural Resources rates the Lake Mendota watershed as a high priority for surface water protection and research.[i] Scientists have observed a change in the crayfish distribution in the Lake’s watershed where the indigenous species are being displaced by invasive crayfish. The impacts of invasive species pose a threat to the quality of aquatic habitat by destroying vegetation and disrupting fish habitat.

Development along waterways in the Lake Mendota watershed is likely impacting crayfish habitat. The confounding effects of land cover change make assessing the relationship between crayfish and their surrounding environmental variables difficult. Developing a method based on ecological factors that can distinguish aquatic habitat for native crayfish from habitat at risk of invasion is our goal.

Study Area

Our research area is the watershed of Lake Mendota in Dane County, Wisconsin. The Lake itself will be excluded from the analysis due the lack of field samples for crayfish habitat. The aquatic habitat in rivers, where the field samples were taken, will be the focus of analysis for the project. From west to east, the rivers that make up the in-flow to Lake Mendota are the: Pheasant Branch, Dorn Creek, Six-mile Creek, Yahara and Token Creek. Pheasant Branch and Dorn Creek are useful study areas for assessing the impact of recent development. Six-mile Creek and Token Creek, with less development and a more meandering course, are useful for distinguishing the other factors from development impacts.

Proposed Tasks

1) The crayfish samples and observed habitat will be plotted onto a data layer as points locations. The determination environmental conditions will take place at each point.

2) Then from each of the following data layers variables will be created, each with their measure of the amount or degree that each environmental factors occur for the field sampling points.

The soil data layer will be overlayed with the 1:24,000 DNR river shape file to create a river substrate model, showing what kinds of soils are likely to be located on river bottoms
A panchromatic QuickBird Image will be classified to show water clarity and the presence or absence of aquatic vegetation.
Recent land-use maps will be used to determine where new construction has taken place. Then the determined newly constructed areas calculated as a proportion of the total surface area that they make up for that river basin, giving a measure of the amount of land use change.
FEMA floodplain maps will be digitized to show the floodplain extent showing the amount of crayfish habitat that is potentially available.
From the river layer, river sinuosity will be calculated by comparing the river miles covered to the Euclidean distance from the headwater to the mouth.

3) The environmental factors (river substrate, run-off, aquatic vegetation, the proportion of the watershed under recent construction, and river sinuosity) will then be gauged with respect to each of the crayfish field sampling points to create a series of measures for each field location.

4) Field locations will then be compared to one another to evaluate the degree to which each of environmental factors is present for that location. As trends for all of the crayfish field sites will be compiled, it is possible to determine a divergence between the kinds of environmental factors favored by invasive crayfish compared to native crayfish.

5) The project output will consist of: 1. A table spelling out the matrix of environmental factors for each field site included with a short report on environmental factors as they related to observed crayfish habitat; 2. Thematic maps for each of the data layers.

These will help determine if there are consistent trends between observed crayfish habitat and environmental factors and to what degree these environmental factors differ between native and invasive crayfish locations?