Coastal movements of a Critically Endangered wedgefish species and the importance of transboundary conservation

Wedgefishes represent a threatened group of elasmobranchs with limited knowledge on their ecology and habitat use. To improve our understanding on their movement ecology, 28 whitespotted wedgefish Rhynchobatus djiddensis were acoustically tracked for up to seven years along ~900 km of the South African and Mozambican coastline. While detection rates were low, some site fidelity was evident (most detections occurred within 50 km of tagging location). However, there was intraspecific variability in the scales of movement, with individuals tagged in the northern extent of the study region displaying restricted movements (< 100 km), while individuals tagged in the southern extent made significant longshore movements (up to ~500 km). Movements lacked seasonal trends in directionality, suggesting they were not migrations, and the drivers of these movements remain unresolved. This study confirmed for the first time that whitespotted wedgefish undertake transboundary movements between South Africa and Mozambique, highlighting the need for international cooperation between the countries that have neighboring Marine Protected Areas.