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

Abstract

The routine assessment and monitoring of aquatic habitat characteristics, such as submerged aquatic vegetation (SAV), is a fundamental tool in fisheries management. The relative low cost and availability of recreation‐grade side‐scan sonar (SSS) systems has made capturing high‐resolution (<10 cm) underwater imagery a practical and viable tool for improving these assessments. Using Humminbird SSS and a boat‐mounted transducer, we determined our ability to produce classified maps of SAV within three reservoirs in Texas. Sonar recordings of photic zone habitat were collected and processed into georeferenced mosaic images by using SonarTRX SSS software for use in geographical information systems (GISs). The resulting raster images were interpreted to identify and map SAV, and a classification scheme was developed. Random‐point data was also used to develop a traditional error matrix and an accuracy assessment for each classified map. In the three reservoirs, 485 ha were classified, including 298 ha of SAV. The area estimates for 11 of 12 classes fell within the 95% CIs that were estimated from concurrent random‐point surveys. Overall classification accuracy ranged from 78% to 88% for the three reservoirs. The methods that were developed demonstrate an accurate procedure for calculating SAV coverage and producing a high‐quality map product for distribution to stakeholders.

A Review of Remote Sensing of Submerged Aquatic Vegetation for Non-Specialists

“…A single beam echosounder produces transects of data (Figure 7), while a multibeam echosounder can create acoustic images with two dimensions of pixels [33]. Side scanners also produce acoustic images and are especially effective in macrophyte studies as their horizontal plane intersects vertically growing plants [33,69,70].…”

“…A single beam echosounder produces transects of data (Figure 7), while a multibeam echosounder can create acoustic images with two dimensions of pixels [33]. Side scanners also produce acoustic images and are especially effective in macrophyte studies as their horizontal plane intersects vertically growing plants [33,69,70]. The exclusively positional data provided by acoustic sensors cannot provide information about the species, health or maturity of vegetation; the applications of such sensors are thus limited to structural information.…”

“…It has been found that hydroacoustic methods produce higher SAV height and percent cover measurements than those from divers or imagery. Hydroacoustic methods may therefore not capture modest changes in SAV conditions and are not suited to direct comparison with data gathered through other methods [70,90]. Still, ongoing innovations in hydroacoustic RS-such as the Dual-frequency Identification Sonar, which produces acoustic video footage-are expected to make acoustic RS more appealing and accessible for work in turbid waters [33].…”

Open-source approach for reproducible substrate mapping using semantic segmentation on recreation-grade side scan sonar datasets

“…Recreation-grade SSS instruments have enabled scientists to manually and semi-manually map the benthos. Applications include mapping large wood (Kaeser and Litts, 2008;Holcomb et al, 2020), substrate (Kaeser and Litts, 2010;Kaeser et al, 2013;Cheek et al, 2016;Walker and Alford, 2016;Scholl et al, 2021), meso-habitats (Smit and Kaeser, 2016;Kaeser et al, 2019), fish abundance (Bollinger and Kline, 2017;Lawson et al, 2020;Wolfenkoehler et al, 2023), and aquatic vegetation (Bennett et al, 2020).…”