Post by Victoria Starnes.— Hi, I’m Victoria, the newest graduate student in the Fisheries Management and Aquatic Conservation lab at Mississippi State University. My project will focus on Bluff Lake, a 1,200-acre shallow lake located on the Sam D. Hamilton National Wildlife Refuge. This lake undergoes seasonal drawdowns which help provide food resources for a diverse array of birds including migrating ducks, egrets, herons, and wood storks (To see some of these birds in action at the refuge, check out this video. Although these drawdowns are beneficial to wildlife very little is known about the impact of the drawdowns on water quality, habitat availability, the sportfish community, or even the effect on fishing.

Right now, I’m working on modeling how available habitat changes with these seasonal drawdowns. A simple way to do this is though bathymetric mapping, which is creating a map of the bottom of the lake similar to a topographic map. To create this map, I am using a Humminbird 1198c, which is basically a really fancy fish-finder that uses sonar to produce images of the lake bottom. The data collection itself is actually quite simple. The Humminbird can be set to record depth and other measurements while on the water. Then, lateral and longitudinal transects at 20-meter intervals are driven across the lake (Check out my technician Rick driving his first transect in the image below!).

The data can then be pieced together using SonarTRX or another similar map-building software which stitches together the transects to create a map. After creating a map of the lake at its highest level and collecting information on the water elevation, I aim to model the different habitats that are available at any given lake level (Check out the awesome example below that I drew in Paint. Don’t worry, I’ll add better examples later!).

I can then pair this model of the lake bottom with other data collected, including data from water quality and fish surveys, to get an idea of how these factors are interacting over the course of the drawdowns. Hopefully the results of my research will provide insight as to the ecological impacts of seasonal drawdowns so that managers at Sam D. Hamilton National Wildlife Refuge can make more informed management decisions and maintain the difficult balance of managing Bluff Lake for both fish and wildlife.

Check back later to learn more about what I’m doing next for the project!