As coastal regions become more developed with harbours, shipping activity and marine renewable energy developments, it is important to understand possible impacts on species of conservation importance. Gaps have been identified in our understanding of the movements of migratory fish species within coastal regions. Accordingly, a SEACAMS2 project was established between industry and academia to develop an autonomous maritime vehicle to actively track acoustically tagged fish. This presentation outlines the system currently under development and the aspirations for its future application.

Samples from a triangular array of hydrophones are digitized by a Turbulent Research “ORCA” board. These samples are sent to a Beaglebone Black embedded processor. The Beaglebone calculates estimates of the time difference of arrival of the acoustic tag signals at the hydrophones. Those delay estimates are then processed to yield an estimate of the distance and bearing to the tag. These range and bearing data are fed into the vehicle tracking algorithm, in order for the vehicle to follow the subject while maintaining a safe distance, so as not to disturb the individual’s natural behaviour.

The work presented here will focus in particular on evaluating different methods for estimating the range and bearing from the delay estimates and will study the behaviour of the system if the assumption of co-planarity of the maritime vehicle and target is violated. Initial testing will use small spotted cat sharks as they are in abundance, before moving on to migratory species, such as salmon and sea trout.