A method for estimating the “position accuracy” of acoustic fish tags

Abstract

Acoustic tag systems have been used for many years to study the behavior of fish in specific areas of interest. In particular tag systems are being used successfully to study the behavior of downstream migrating salmon smolts ( Oncorhynchus spp.) as they approach hydro-electric dams. While field studies have demonstrated the potential for acoustic tag systems, little has been done to quantify their performance. This paper develops a method for predicting the accuracy of the “position estimates” provided by acoustic tag systems. General expressions are developed that can be applied to any particular deployment of a tag system which lead onto a method for the direct calculation of the “position error” as a function of hydrophone geometry, standard deviation of the signal arrival times, and the inaccuracies in the assumed sound velocities. This method is independent of the algorithm used to determine the position solution. Using the methods of analysis developed here some specific examples are presented that provide general guidelines that should be followed to achieve good performance when deploying an acoustic tag system.