Big Indiana Bass

Anglers have a new toy to play with, as you've probably already become well aware. Seems like you can't go on an electronics fishing forum without multitudes of posts and pictures from guys using their Hummingbird sidescan sonar units. Maybe it's just sour grapes coming from a dedicated Lowrance junkie, but I frequently refer to such users in jest as the "Look, I found a tree!" crowd. That said, there is lots of potential for these units as more people continue to purchase and utilize them out on the water, and as technology and reliability get better and better. 

One of the common misperceptions is that these are the same units used by state and local agencies to find ditched cars and solve unexplained disappearances. Or that these ultra-detailed topographic maps being created and distributed are done so with the same units guys fish with on their bass boats. In most cases, the serious work is being done with very high tech units costing upwards of $70,000 or more from other companies. A recently published article in Fisheries Magazine might be the beginning of high tech/low cost alternative uses for these units.

In "An Assessment of Deadhead Logs and Large Woody Debris Using Side Scan Sonar and Field Surveys in Streams of Southwest Georgia", researchers used common, everyday bass gear to survey large stretches of a Georgia river system to document how much woody debri from old logging operations were present throughout the watershed. Some of the equipment and techniques were as follows:

• "We employed a Humminbird® 981c SI system to capture sonar imagery at all study reaches"
• "The SI system was connected to the Garmin GPSMAP® 76 GPS to provide coordinate information for image capture locations, at a stated accuracy of 3–5 meters (Garmin 2006)."
• "The sonar transducer was aft-mounted to the port side of a johnboat transom, and its frequency set at 455 kHz during sonar surveys."
• "The sonar range was set to 65 feet during the survey of Chickasawhatchee Creek and 80 feet during the survey of Ichawaynochaway Creek."
• "Coordinate data and sonar images were simultaneously recorded to the SI system during the survey. These data were recorded at regular intervals such that consecutive overlapping images were acquired."
• "Prior to the surveys, targeting exercises were conducted with a piece of PVC pipe (length 1.7 m, diameter 11 cm) submerged in various locations to evaluate our ability to image LWD-like objects."
• "Using Microsoft (MS) PowerPoint, we spliced overlapping sonar images together to produce a seamless mosaic for each study reach."

Researchers Adam J. Kaeser and Thomas L. Litts summarized:

Side scan sonar facilitates wood surveys across broad aquatic landscapes, enabling the examination of factors affecting the spatial and temporal patterns of wood distribution, and ecological associations (e.g., patterns of stream productivity), in ways deemed logistically unfeasible in the past. The applications of side scan sonar for mapping stream habitat extend well beyond woody debris. Our current work with the Humminbird® SI system includes GIS applications such as image geotransformation and mapping of stream substrates, topics we intend to present in forthcoming manuscripts. We hope that this research encourages scientists and managers to consider mapping, monitoring, and assessing stream habitat with low-cost side scan sonar, and suggest that future research evaluate the use of side scan sonar elsewhere to explore the effective boundaries of this
remote sensing technique.