Linking Low-Cost Side Scan Sonar Habitat Data with Occupancy-Based Population Models

The use of low-cost side scan sonar has provided a wealth of fine-scale habitat data. However, these data have not been fully integrated into assessments of stream fish demographics or occupancy patterns. Here we present the results of two modeling exercises focused on Guadalupe Bass, Largemouth Bass, and Gray Redhorse populations in central Texas. We conducted side scan sonar surveys along the entire length of the South Llano River and classified substrates and mesohabitat types. Point surveys of the fish assemblage were conducted at 70 randomly-selected sites. We used a single season, two species occupancy model to assess the instream habitat factors that influence occupancy of Guadalupe Bass and Largemouth Bass as well as determine the relative importance of potential interspecific interactions on their occupancy patterns. We also conducted a multiple season mark-recapture survey of Guadalupe Bass and Gray Redhorse. A robust design model was constructed to assess the influence of instream habitat factors on the movement, mortality, and population size of Guadalupe Bass and Gray Redhorse using the mark-recapture data. Instream habitat data collected using low-cost side scan sonar provided additional insights into the population dynamics of our study species that would not have been available using other approaches.