Use of a novel acoustic 'listening' method for detecting pump impellor strike on downstream migrating eels

Abstract

Fish mortality through floodplain pumping stations is a recognised global issue, but few studies have quantified the degree of mortality that occurs during pumping. We investigated the potential of passive acoustic monitoring (PAM) as a tool to record sounds made by fish and their likely mortality as they passed through pumps during downstream migration. The acoustic properties made by freshly killed eels that were fed through an existing pump station were compared to those made by goldfish (Carassius auratus). Processing and analysis of acoustic data enabled the development of an ‘eel-specific’ algorithm for detecting eels passing through the pumping station. The duration of sound and filtered intensity were useful characteristics enabling reliable separation of the two fish species. The algorithm was then applied retrospectively to soundscape recordings obtained during a typical eel migration period at the test site. Although the tool is unlikely to be able to differentiate the sound of goldfish from ‘other’ potential sounds of short duration (e.g. sticks), differentiating eels from other sounds was demonstrated. We conclude that this tool has considerable potential for improving the understanding of the timing of eel migrations and likely mortality through pumping stations. The tool may also be used to inform the development of both remote and manual pump management options for reducing pump-related eel mortality.