Standard Talk (15 mins) Australian Society for Fish Biology Conference 2022

A drone-based application for assessing abundance of a pelagic fish in shallow coastal waters (#73)

Jason Earl 1 , Damian Matthews 1
  1. SARDI Aquatic and Livestock Sciences, West Beach, SA, Australia

Reliable estimates of relative abundance are fundamental to fishery stock assessments. Fish abundance indices derived from fishery-dependent data have some utility but are often confounded by changes in fishing practices, fleet dynamics and other factors (e.g. markets). Fishery-independent sampling of fish populations can provide useful abundance data but is often expensive and logistically challenging to undertake. The recent proliferation of unmanned aerial vehicles (UAVs, drones) in wildlife research has provided a promising new platform for aerial surveys of coastal populations of pelagic fish, especially those that spend part of their life near the surface. Western Australian salmon (Arripis truttaceus) is an abundant medium-sized schooling pelagic fish species, endemic to the temperate coastal waters of south-western Australia where it supports important commercial and recreational fisheries. Large schools of salmon migrate from South Australia to Western Australia. This study investigated the utility of aerial surveys using a low-cost, consumer grade drone for determining relative abundance of WA salmon. Aerial surveys were undertaken along 3-km transect at twelve beaches on the west coast of South Australia in August and November 2021. Post hoc analysis of drone video footage revealed that schools of salmon of varying sizes and densities could be reliably sighted in multiple survey habitats using the UAV.  Water depth, turbidity and wind speed significantly impaired detection of salmon schools. Our preliminary findings suggest that drones could provide a cost-effective aerial survey tool to reliably estimate relative abundance for fish populations in shallow coastal waters.