Over 90% of great and scalloped hammerheads had died before landing during a survey of the U.S. Two of the more prominent species of this family are the great and scalloped hammerheads, Sphyrna mokarran and Sphyrna lewini. One group of species that exemplifies these challenges during handling times are the hammerhead sharks (family Sphyrnidae) due to their low stress tolerance caused by a fast build-up of stress related metabolites. However, the need to physically catch and restrain a shark inevitably elicits a physiological stress response, which can have detrimental impacts on the animal. Due to their ability to transmit data to orbiting satellites from which the data can be accessed directly, fin-mounted satellite-linked geolocators offer an option to remotely collect accurate horizontal movement data of animals that undergo long-distance migrations, such as large-bodied sharks (reviewed by ).ĭespite a wide variety of forms, sizes, and fastening mechanisms available, mounting satellite-linked geolocators toward the tip of the shark’s dorsal fin requires the shark to be caught and temporarily restrained for the drilling of one or more holes using a template for the positioning of the geolocator bolts. Understanding animal movements is crucial if we want to advance our knowledge about habitat use, niche partitioning and anthropogenic disturbances and to design conservation management measures (reviewed by ). As such, the 4-hole drill attachment makes the mounting process faster and more reliable and should reduce the stress experienced by the animal. Simultaneously drilling four holes reduces the need to keep the animal’s fin steady for an extended period of time and thus makes the deployment of fin-mounted geolocators less dependent on the animal’s behavior and the weather conditions. The new drill attachment further allowed the successful tagging of a great hammerhead alongside a research vessel in rough seas that would have made the deployment using traditional protocols more challenging. The time required to secure the geolocators, from drill alignment to the complete fastening of the last bolt, ranged from 68 to 85 s (78.2 ± 10.9 s, mean ± SD). The drill attachment was successfully tested on four great and two scalloped hammerheads, Sphyrna mokarran and Sphyrna lewini, which were all tagged with 4-bolt Smart Position and Temperature (SPOT) tags. Here, we present the plans for a drill attachment allowing the template-free drilling of up to four holes simultaneously for a faster, more accurate and safer deployment of fin-mounted geolocators. However, the deployment protocols of such geolocators, which normally consist of drilling one to multiple holes using a template, can be challenging, and depending on the animal’s stress physiology and ocean conditions, speed and accuracy may be crucial. Fin-mounted geolocators are widely used in marine studies to track animal movements and to design informed management strategies.
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