Initial studies of marine animals were dependent on direct observation of subject species, which required access to the animals in the wild or captive environments. However, the lifecycles of many marine species occur solely or partially outside of the observable realm of researchers, animals undertake movements or behaviors that cannot be studied in captive systems, or they cannot be appropriately maintained in captive facilities. The advent of animal-borne tags has provided an avenue to study some of these previously unobservable states. Initial acoustic and satellite tags provided information about the presence/absence, horizontal movements, vertical distribution, and temperature preferences of study animals [1, 2]. Advances in miniaturization of biologging tags (e.g., with accelerometers, magnetometers, heart-rate sensors, cameras, etc.) support increasingly complex studies of animals’ movements, behaviors, physiology, and/or their environment (see [3, 4]).
A combination of recent advances in biologging technologies has the potential to record previously unobservable states in the most secretive and difficult to study species. Especially large sharks, where capture is either not feasible or dangerous to animal or researcher, require methodological solutions since successful use of many biologging tags requires a rigid or predictable attachment on the animal. Traditional external shark tags (acoustic and pop-off satellite) are typically attached to animals via a flexible tether and a subcutaneous dart, which allows the tags to “wobble” as the animal swims. This action of the tags masks the changes in animal movement making them indistinguishable from tag movement. This wobble also presents significant challenges for frame stability and consistent focus on the area of interest when cameras are included. As a result, rigid mounts have typically required capture (i.e., with hook and line) and restraint of the animal either in the water or onboard a vessel , which can have significant physiological consequences for the animals [6, 7]. Additionally, though the tags often aim to continuously record the natural behaviors of the animal, the animals’ behaviors can be significantly influenced by the stress of capture/restraint [8, 9].
Gleiss et al.  introduced a clamp-tagging method on whale sharks (Rhincodon typus) that rigidly applied biologging tags via a specially designed tagging pole. Though this method works well for some large animals, characteristics of their methods preclude the use of these techniques with large predatory sharks. First, Gleiss et al.  swam with the whale sharks and applied the biologging tags underwater directly to the shark’s fin. As white sharks (Carcharodon carcharias) are the largest predatory fish in the oceans, free-swimming with them to deploy tags presents a significant risk to researchers. Secondly, Gleiss et al.  used clamps with 1.5-cm barbs to provide the anchoring of the units to the second dorsal fins. Though Gleiss et al.  found little effect from the tagging on the second dorsal fin of whale sharks, for white sharks, these biologging tags, which generally range in size from 100 to 500 g, must be placed on the first dorsal fin. These fins are biologically critical for stability while fast swimming  and are used scientifically as means to uniquely identify individuals across decades  and estimate abundance [13, 14]. Additionally, some communities are dependent on white sharks for ecotourism, so there are sensitivities to the risk (or perceived risk) of damage to dorsal fins from attaching data loggers . Therefore, attaching tags to the dorsal fin  could have significant biological and economic consequences that must be limited.
Therefore, it is advantageous to develop a method to attach biologging tags to large predatory sharks without catching or restraining the animals and with limited negative effects. To address this, we designed a modified rigid non-invasive fin clamp and attachment technique, based on Gleiss et al. , to deploy biologging tags on free-swimming white sharks. We attached these clamps, coupled with biologgers, at seasonal aggregation sites in Gansbaai, South Africa. This is the first time that this combination of sensors and attachment has been used on large white sharks. These methods do not require catching or restraining the animals, presenting an alternative method to rigidly attach biologging tags on large predatory marine animals while they free-swim with little risk to researchers, target species, and their recorded behaviors.