Validation of a Side‐Scan Sonar Method for Quantifying Walleye Spawning Habitat Availability in the Littoral Zone of Northern Wisconsin Lakes

Abstract

Previous research has generally ignored the potential effects of spawning habitat availability and quality on recruitment of Walleye Sander vitreus, largely because information on spawning habitat is lacking for many lakes. Furthermore, traditional transect‐based methods used to describe habitat are time and labor intensive. Our objectives were to determine if side‐scan sonar could be used to accurately classify Walleye spawning habitat in the nearshore littoral zone and provide lakewide estimates of spawning habitat availability similar to estimates obtained from a transect–quadrat‐based method. Based on assessments completed on 16 northern Wisconsin lakes, interpretation of side‐scan sonar images resulted in correct identification of substrate size‐class for 93% (177 of 191) of selected locations and all incorrect classifications were within ± 1 class of the correct substrate size‐class. Gravel, cobble, and rubble substrates were incorrectly identified from side‐scan images in only two instances (1% misclassification), suggesting that side‐scan sonar can be used to accurately identify preferred Walleye spawning substrates. Additionally, we detected no significant differences in estimates of lakewide littoral zone substrate compositions estimated using side‐scan sonar and a traditional transect–quadrat‐based method. Our results indicate that side‐scan sonar offers a practical, accurate, and efficient technique for assessing substrate composition and quantifying potential Walleye spawning habitat in the nearshore littoral zone of north temperate lakes. Received December 1, 2015; accepted March 24, 2016 Published online July 20, 2016

Use of Wind Fetch and Shoreline Relief to Predict Nearshore Substrate Composition in a North Temperate Lake

“…The ability to effectively predict shoal substrates and the effect of wind-wave energy may allow for the identification of existing spawning locations and areas for habitat protection. Although other techniques can be used to assess available substrates (Richter et al 2016;Walker and Alford 2016), development of a predictive tool can allow for rapid application over multiple waterbodies and for determining how environmental factors could influence substrate modification projects. Shoreline areas meeting specific wave velocity and substrate criteria can be targeted via this approach to provide the most efficient use of limited resources when conducting habitat improvement projects.…”

“…Identifying the location of preferred spawning substrate, conducting habitat improvement projects, and establishing refuges are common efforts to improve spawning potential (Robillard and Marsden 2001;Bozek et al 2002;Dustin and Jacobson 2003;Katt et al 2011). To address these habitat concerns, managers not only need information on the condition of the substrates (Richter et al 2016;Walker and Alford 2016) but also require information on how they are influenced and distributed by environmental factors.…”

Using Recreation‐Grade Side‐Scan Sonar to Produce Classified Maps of Submerged Aquatic Vegetation

“…The acquisition of this user-friendly technology, coupled with the widespread integration of GPS and GIS technologies, has enabled scientists to record and spatially display sonar imagery that covers a greater extent of underwater habitat. To date, recreation-grade SSS has primarily been used by fisheries managers to map and characterize underwater structures such as woody debris and substrate Litts 2008, 2010;Richter et al 2016;Buscombe 2017) and more recently large (>1 m) freshwater organisms such as manatees Trichechus spp. (Gonzalez-Socoloske and Olivera-Gomez 2012), sturgeon Acipenser spp.…”

Using GIS to predict habitat in lakes: An example using nearshore substrate categories

“…Quantification via side scan sonar has become increasingly popular. The cost of units has decreased, methods have been developed and tested across systems, data can be collected continuously, and the process is faster than transect‐based methods (Kaeser and Litts ; Kaeser et al ; Richter et al ; Graham et al ). However, it still requires data collection in the field, postprocessing expertise, and field validation (Kaeser and Litts ; Graham et al ).…”

“…Furthermore, neither of these methods directly associates the spatial locations of habitats to environmental factors that may be structuring their distributions. Understanding the factors that structure habitats such as substrates is key to their management (Richter et al ). Therefore, the need to develop additional methods for habitat quantification still exists (Fisher et al ).…”