Hydroacoustic techniques use underwater sound signals to identify fish and are widely applied in pelagic species surveys, with recent adaptations for demersal fish such as snapper (Chrysophrys auratus). Traditional hydroacoustic surveys rely on crewed vessels, but engine noise can induce fish avoidance behaviour, potentially biasing biomass estimates. Autonomous surface vehicles (ASVs) offer a quieter, scalable, and cost-effective alternative, reducing disturbance and enabling more consistent data collection.
In January 2025, CSIRO and the South Australian Research and Development Institute (SARDI) conducted a field experiment in Gulf St Vincent, South Australia, to evaluate ASV-based hydroacoustic surveys. The study deployed the Maritime Robotics Otter ASV, equipped with a Simrad ES38-18/200-18C echosounder and WBT Mini transceiver, alongside a crewed vessel using identical survey protocols. The ASV surveyed first, followed immediately by the crewed vessel, allowing direct comparison of target strength distributions, fish density estimates, and acoustic noise profiles.
Results and analysis comparing ASV-based survey techniques with traditional methods in terms of detectability, cost, and practicality will be presented. Additionally, the future prospects of autonomous hydroacoustic surveys for scalable and efficient stock assessments will be discussed, with a focus on refining autonomous survey methodologies, integrating adaptive mission planning, and establishing best practices for ASV-based assessments.