Accuracy and Precision of Hydroacoustic Estimate of Aquatic Vegetation and the Repeatability of Whole-Lake Surveys: Field Tests with a Commercial Echosounder

摘要

Submersed aquatic vegetation provides critical habitat for numerous Minnesota fish species and is an integral component of fish community integrity (Valley et al. 2004; Drake and Valley 2005). The cumulative effects of lakeshore and watershed development has had negative effects on fish communities in the upper Midwest (Christensen et al. 1996; Jennings et al. 1999; Radomski and Goeman 2001; Drake and Valley 2005). Unfortunately, habitat assessment techniques have lagged behind impacts occurring to lake habitats, and spatially explicit quantitative data on the distribution of aquatic vegetation in lakes is lacking. Hydroacoustics coupled with differentially corrected GPS, analyzed in a GIS represents a promising new tool in the acquisition of important habitat data (Valley et al. 2005). Hydroacoustics has been an effective tool for assessing the abundance of submersed aquatic vegetation for some time (Maceina and Shireman 1980; Duarte 1987; Thomas et al. 1990). However, until the advent of global positioning systems (GPS) in the 1990s, our abilities to map the distribution of vegetation was greatly limited. Sabol and Melton (1995) describe an automated hydroacoustic system coupled with GPS to estimate bottom depth, vegetation cover, and vegetation height at numerous georeferenced locations. This system (a BioSonics Inc. digital echosounder, GPS, and bottom/plant detection algorithm) was originally termed the Submersed Aquatic Vegetation Early Warning System (SAVEWS; Sabol and Melton 1995). Tests on the performance of this system and algorithm have been performed in some hard bottom riverine and estuarine systems, and demonstrated high precision and accuracy in those environments (Sabol and Johnston 2001; Sabol et al. 2002a,b).