Results of a pilot study using acoustic telemetry to assess the movements of coastal elasmobranchs in Namibia’s only marine protected area

Abstract

Many elasmobranch (shark, skate and ray) species inhabit the Namibian Islands Marine Protected Area (NIMPA), but little is known about the home ranges and movements of these species. Such information is essential for understanding whether a marine protected area provides effective protection to species of conservation concern. This study describes the first effort to tag and acoustically track three elasmobranch species in Namibian waters. A total of eleven individuals of three species – Mustelus palumbes, Acroteriobatus blochii and Raja straeleni – were tagged in February 2023. Three acoustic receivers were deployed at sites in the vicinity of Lüderitz Bay and a fourth was deployed further south, in Grosse Bucht. Data collected over 12 months revealed some of the smallscale movements of nine of the eleven tagged animals, but the limited spatial coverage provided by the four receivers was not enough to fully describe the movement behaviours of these animals. Nonetheless, this research – the first study to internally tag and track chondrichthyans in Namibian waters – has revealed how tracking studies can contribute valuable data that can inform the management and protection of mobile species like sharks, skates and rays, and the design of future marine protected areas.