Photogrammetric counts of pacific salmon by means of unmanned aerial vehicles of consumer grade

Abstract

Methodology for photogrammetric counting of pacific salmon by means of unmanned aerial vehicles (UAVs) of consumer grade is developed. The spawners and spawning redds are counted using photogrammetric processing of aerial images taken by UAVs at monitoring sites. The photogrammetric products (orthomosaics and digital elevation models — DEMs) are analyzed in geographic information systems (GIS). The estimations of relative abundance for the monitoring sites are extrapolated to entire area of potential spawning grounds. There is shown for the first time that DEMs of water channels allow to visualize and count the redds. Detailed description of methodology is presented, including the survey planning and implementation, data processing, fish abundance estimation, data analysis and visualization, and web-publication. Recommendations for choosing UAV, its accessories and software for flight, photogrammetry and GIS are provided. This approach will facilitate objectivity of salmon counts and provide gradual transition from subjective aerovisual methods towards proven and verified digital basis of fish abundance assessment.