Design and Performance of an Autonomous Video Counting Tower to Monitor Salmon Escapement on Remote Streams

Aerial surveys and counting towers are often used in Alaska to monitor the run timing and abundance of adult salmon migrating upstream to spawn.  However, neither method provides a reliable absolute abundance estimate of total escapement, which is a key input for the spawner-recruit models frequently used to evaluate escapement goals.  In 1996, the Alaska Department of Fish and Game began developing an autonomous remote video system to deploy on streams with modest escapements that don’t merit the expense of weir or sonar based enumeration systems.  The remote video system is designed to operate continuously on 12 volt batteries that can be recharged by solar, wind, or hydro-generators.  The entire system is self-contained on a quadrapod that protects the equipment from bears and floods and allows placement at the most appropriate location for counting fish.   Digital time-lapse images are captured in the field onto a hard drive that is periodically retrieved for processing, but can also be set up for remote access and real-time monitoring via microwave or satellite transceivers.  Daily escapement counts derived by remote video were nearly identical to weir counts when the two methods were operated concurrently (R² > 0.98).  The reliability and performance of the system has led fishery biologists in Alaska to begin using video-derived escapement data for more precise in-season management of commercial fisheries. This presentation will provide details on system design, equipment, and desirable site conditions necessary for the successful operation of autonomous video counting towers for remotely monitoring salmon escapement.