Identifying redds from the air is a bit different from traditional on-the-ground methods, with unique nuance that requires specific training and some experience. Last year, we highlighted how IDFG identifies redds from an aerial perspective in this vlog, with specific examples of redds counted in the Upper Salmon River during the 2023 spawning ground surveys. 

So, how exactly do we do it? Once in the air, the drones do most of the work, flying the river corridor around 150 feet in the air at nearly 12 miles per hour, photographing the streambed every 30 feet or so. As pilots, we are tasked with identifying hazards, and ensuring each survey is carried out safely. The images are stored on memory cards within the drone, so the actual identification and counting of redds happens after the survey. 

Back at the office, two pilots go through all the images and count redds independently, as a means to “double check” one another. The official count offers information about spawner abundance, which is crucial when monitoring fish populations. Although, to put a year of redd counts into perspective we must compare them to something. We do this by comparing the current years count to previous years averages, dating back to when populations were considered healthy. This way, by sampling every year using the same techniques, around the same time, and in the same places, we can identify trends in abundance for a highly variable fish species like Chinook Salmon.