A new publication in Animal Biotelemetry describes how a free-swimming one Great White Shark (Carcharodon carcharias) before Canada was equipped with a satellite transmitter on the dorsal fin without first fishing the animal, fixing it alongside or lifting it out of the water. The work documents a technical approach that could reduce the burden on large sharks when fitted with radio collars.
The test animal was a female great white shark named Salvager, approximately 14 feet or 4.3 meters long. She swam at remote islands off the southwest tip of Nova Scotia in the fall of 2025. According to the Shark Research Foundation, she was the first free-swimming great white shark in Canadian waters to receive a fin-mounted satellite transmitter in this way.
Why transmitters on the dorsal fin are valuable
Satellite transmitters on the dorsal fin can transmit data when the fin breaks the water surface while swimming. This creates position reports over a longer period of time without the animal having to be found again or the transmitter having to be recovered. For a highly migratory species like the great white shark, this data can reveal whereabouts, seasonal routes and connections between coastal regions.
Traditionally, such transmitters are often installed after a shark has been brought to a ship with bait and hooks and inspected there for installation. This enables precise work and additional measurements, but means catching, handling and temporarily restricting freedom of movement. For very large animals, the logistical effort is also considerable.
CO₂ applicator instead of hooks and fixation
Neil Hammerschlag of the Shark Research Foundation adapted a remote-controlled tagging system originally developed for whales and dolphins. A veterinary applicator powered by CO₂ was used. It accelerates the attachment to the dorsal fin from a distance.
The satellite transmitter was anchored in the fin with titanium arrows. It is not only important to hit the target: the angle, distance, energy and attachment must be selected so that the transmitter sits securely without penetrating unnecessarily deeply. The publication is therefore primarily a technical case documentation – not a statement that the procedure has already proven itself in many animals and under all conditions.
The practical advantage is obvious: the shark does not have to have bitten and does not have to be held on the boat. This can shorten the time in close proximity to the ship and avoid the stressors caused by fatigue, restraint and handling. At the same time, the long-distance shot requires very experienced teams, calm conditions and a good view of the dorsal fin.
Salvager initially stayed in the region
The Shark Research Foundation After marking, reported that Salvager initially stayed mostly near the outer islands where it had been tagged. Later she also swam in the Bay of Fundy. The positions received almost in real time indicate that the island region could play an important role for this individual animal.
However, a general key habitat for the entire population cannot be derived from the route of a single shark. This requires more animals, longer running times and comparisons between years, genders and age groups. Salvager’s data first shows that the technical chain of attachment, broadcast and public display basically works.
Less invasive does not mean no intervention
The method is described as non-invasive or non-catching because the shark is not hooked and restrained. However, it is not entirely without physical intervention: the titanium anchors penetrate tissue in the dorsal fin and the transmitter creates additional resistance. How long the attachment lasts and how the fin reacts in the long term must therefore be documented, as must the quality of the position data.
Several metrics are important for a reliable assessment: hit and attachment rate, duration of transfer, wound healing, possible behavioral reactions and a comparison with established procedures. Missed shots or incomplete fortifications also belong in such a balance sheet. Only repeated operations can show under which sea and visibility conditions the technology is reliable and justifiable.
A tool for research on large sharks
The first mission in Canada is therefore less of an end point than a starting point. If the technology can be standardized, researchers could also tag large or cautious sharks that cannot be safely caught and kept alongside. This would expand the range of individuals that can be examined and potentially reduce capture-related biases in movement data.
Such data is particularly valuable for the protection of great white sharks. Only if it is known which areas they regularly use, when they move between regions and where individual life phases are concentrated can shipping traffic, fishing and other human activities be better assessed spatially and temporally. Salvager’s transmitter provides a new data window and at the same time a practical test of how modern biotelemetry can get by with less catching and handling.
