Identifying fish and estimating abundance and swim velocities of migrating Pacific salmon using adaptive resolution imaging sonar in mobile surveys

Abstract Mobile acoustic sounding is an effective survey method for fish abundance residing or migrating in large riverine basins and marine areas. A long-standing challenge in acoustic fish surveys with conventional sonar is the uncertainty in identifying fish targets from acquired echo data. Identification errors of fish targets can significantly bias estimates of fish abundances and negatively impact the management of fisheries. In contrast to conventional sonar, adaptive resolution imaging sonar (ARIS), if deployed properly with appropriate settings, can yield high-quality images of fish targets. ARIS images acquired with adequate frame rates can form video recordings to allow for confident identification of fish targets from recorded morphological features, sizes, direction of movements, and speeds. In this paper, we present an approach of using ARIS sonar for mobile surveys of fish passage in a riverine environment. Applications of this approach are demonstrated for its practical values with results from an ARIS-based mobile survey of upstream migrating salmon at an acoustically challenging fish-counting site on the lower Fraser River in British Columbia, Canada.