An Assessment of Deadhead Logs and Large Woody Debris Using Side Scan Sonar and Field Surveys in Streams of Southwest Georgia

Abstract

Large woody debris provides essential habitat in sand‐bed streams of the southeastern United States. In many Coastal Plain streams, pre‐cut timber, lost more than a century ago during river transport, contributes to the extant large woody debris pool. The extraction of these logs, otherwise known as deadhead logging, threatens habitat integrity in these systems. Little is known of the distribution, abundance, and ecological value of deadhead logs, thus hindering attempts to manage and protect this resource. Moreover, the use of traditional field‐based methods to inventory wood is slow and costly in large turbid streams. Our objectives were to assess wood at several sites in southwest Georgia using traditional methods, then use these data to evaluate the efficacy of quantifying wood using side scan sonar imagery. Deadhead logs were widely distributed and constituted a substantial proportion (> 50% volume and surface area) of the total large woody debris found at study sites. Given these findings, the wholesale removal of deadhead logs could largely impact the ecological integrity of such streams. Analyses revealed strong correlations (r2 = 0.82—0.98) between sonar wood estimates and actual counts suggesting that side scan sonar can be used as a rapid, inexpensive method to quantify wood throughout navigable systems.

Shallow water benthic imaging and substrate characterization using recreational-grade sidescan-sonar

“…However, these inexpensive, lightweight (portable) sidescan sonar units can be deployed on almost any waterborne craft without the requirement of specialist knowledge of sonar and geodetics, and with little to no experience with acoustic remote sensing. This accessibility is behind the rapid increase in popularity of these sonar systems, among the scientific research community for benthic imaging in a range of aquatic environments, both marine and freshwater, lotic and lentic (Kaeser and Litts, 2008;Gonzalez-Socoloske et al, 2009;Collins et al, 2010;Kaeser and Litts, 2010;Havens et al, 2011;Goclowski et al, 2013;Kitchingman et al, 2013;Kaeser et al, 2013;Flowers and Hightower, 2013;Powers et al, 2014;Bilkovic et al, 2014;La Croix and Dashtgard, 2015;Sterrett et al, 2015;Froehlich and Kline, 2015;Buscombe et al, 2015;Cheek et al, 2016;Dunlop et al, 2016;Smit and Kaeser, 2016). Such spatially distributed benthic data are especially important in the development and evaluation of models for habitat suitability and vulnerability (e.g.…”

Spatial Ecology of Female Barbour's Map Turtles(Graptemys barbouri)in Ichawaynochaway Creek, Georgia

“…Four of these female turtles were recaptured under the same two DHLs within the following year. Although we did not make any attempts to discriminate between DHLs (,10.2 m 2 ) and other large woody debris (,2.97 m 2 ; Kaeser and Litts, 2008) with respect to used and random locations, in retrospect, these data may have provided valuable insight into the biological value of deadhead logs in this river system.…”

“…Submerged wood also serves as habitat for prey such as benthic macroinvertebrates (Wallace and Benke, 1984). Large woody debris in Ichawaynochaway Creek comes from both natural and anthropogenic sources (Kaeser and Litts, 2008). Distributed throughout the study area are numerous pre-cut, submerged logs, also referred to as deadhead logs (DHLs).…”

“…Many southeastern U.S. streams can be turbid and non-wadeable during certain times of year, and traditional approaches for measuring habitat features, such as underwater point sampling and extrapolation to estimate available habitat, are typically not feasible. In this study, we assessed the spatial ecology of G. barbouri by quantifying habitat use and habitat availability using side-scanning sonar (Kaeser and Litts, 2008), a recently developed method for mapping instream habitats in non-wadeable streams. This method of habitat mapping, along with radio-telemetry of turtles, allowed us to quantitatively evaluate preferred habitats within a habitat use-availability framework (Manly et al, 2002;Johnson et al, 2006).…”

Estimating Sturgeon Abundance in the Carolinas Using Side‐Scan Sonar

“…Sturgeon and related Paddlefish Polyodon spathula have been identified as potentially suitable targets for hydroacoustic studies (Nealson and Brundage 2007;Bergman 2011;Nelson et al 2013). Side-scan sonar is a relatively old hydroacoustic technology that has been used increasingly in fisheries studies in recent years (Kaeser and Litts 2008;Foote 2009). In a previous paper, we described a procedure to rapidly survey sturgeon populations using side-scan sonar and occupancy modeling approaches (Flowers and Hightower 2013).…”