1. Animal movement studies are conducted to monitor ecosystem health,
understand ecological dynamics and address management and conservation
questions. In marine environments, traditional sampling and monitoring
methods to measure animal movement are invasive, labour intensive,
costly, and measuring movement of many individuals is challenging.
Automated detection and tracking of small-scale movements of many
animals through cameras are possible. However, automated techniques are
largely untested in field conditions, and this is hampering applications
to ecological questions. 2. Here, we aimed to test the ability of
computer vision algorithms to track small-scale movement of many
individuals in videos. We apply the method to track fish movement in the
field and characterize movement behaviour. First, we automated the
detection of a common fisheries species (yellowfin bream, Acanthopagrus
australis) from underwater videos of individuals swimming along a known
movement corridor. We then tracked fish movement with three types of
tracking algorithms (MOSSE, Seq-NMS and SiamMask), and evaluated their
accuracy at characterizing movement. 3. We successfully detected
yellowfin bream in a multi-species assemblage (F1 score = 91%). At
least 120 of the 169 individual bream present in videos were correctly
identified and tracked. The accuracies among the three tracking
architectures varied, with MOSSE and SiamMask achieving an accuracy of
78%, and Seq-NMS 84%. 4. By employing these emerging computer vision
technologies, we demonstrated a non-invasive and reliable approach to
studying fish behaviour by tracking their movement under field
conditions. These cost-effective technologies potentially will allow
future studies to scale-up analysis of movement across many underwater
visual monitoring systems.