Observations of fin injury closure in Great Hammerheads and implications for the use of fin‐mounted geolocators

Objective Sharks face a high risk of injuries throughout all life stages and are therefore expected to show a good wound closure capacity. Methods Here, the wound closure of one major injury and one minor injury to the first dorsal fins of two free‐ranging, mature female Great Hammerheads Sphyrna mokarran is described macroscopically. Result The sharks showed complete wound closure of single, clean‐cut lacerations measuring 24.2 and 11.6 cm in length after an estimated 323 and 138 days. These estimates were based on the observed closure rate and visual confirmation of a complete wound closure upon multiple resightings of the same individuals. Additionally, the posterior lateral displacement of fin‐mounted geolocators within the fin and outside of the fin without causing external damage was documented in three additional Great Hammerheads. Conclusion These observations supplement findings about wound closure capabilities in elasmobranchs. The documented geolocator displacement furthers the discussion about the safe use of these geolocators to track shark movements but also has implications for future tagging studies. Impact statement Given their risk of injuries, understanding wound closure capabilities in sharks is important and is directly relevant to research methods such as the deployment of fin‐mounted transmitters in movement studies. Here, we document the complete closure of first dorsal fin injuries in Great Hammerheads. The recorded shedding pattern of fin‐mounted transmitters without causing external damage furthers the discussion about their safe use and yields implications for future tagging studies.