Shark Tagging: what is it, why do we do it, and how?
Written by Sarah Hayes
Tagging Through The Ages
In the beginning…
Shark tagging and tagging of other animals, has provided us with invaluable information. Identification of animals has been used since as early as the 13th century, when Falcon owners wanted to mark ownership on their birds via name bands (McFarlane et al. 1990). During the early 1900s The Discovery Committee carried out a large tagging project on whales in the Southern Ocean, looking to gather information about life histories and migratory patterns (McFarlane 2015). They used a stainless steel tube with a serial number and offer of reward, inserted via 12-bore shotgun into the whales’ blubber. These original tags (identification tags or other natural or non-natural markings on the body) produced data that could only be collected every time a tag or marking was physically seen. Therefore, researchers were missing very important information of what happens in BETWEEN these sightings.
And then, there was radio…
In the 1950s radio tags were born, and by the late 1960s these tags were used on animals for later re-location using a receiver (Kenward 2000). The downside to radio tags was that the researcher could only find or track the animal when in close proximity to it, but they were at least one step closer to knowing what goes on in BETWEEN sightings! By the early 1980s, satellite tags were being used, and this new form of technology in animal tracking transformed ecological science (Rutz and Hays 2009). Satellite tags were able to provide information not yet obtainable by other means; the animals could be tracked, while the researchers sat in their offices, on dry land, in a whole other country!
Today, researchers can attach a tag to an animal, and record thousands of data points every hour, or even every minute! Tagging not only happens in whales and sharks, but also in Sea Lions (some of the Australian Sea Lions on Hopkins Island have identification tags on their flippers), dolphins, turtles, fish and many land animals too (lions, rhinos, bees, butterflies, cockroaches and monkeys, to name a few). Tagging has provided us with invaluable information on migratory patterns, life histories, movement patterns, social connections, habitat use…the list goes on! This technology is imperative to the research and conservation of animals and ecosystems all around the world!
Great White Shark Tagging
This tag uses specific frequency and transmitting patterns to identify different individuals when passing close to an underwater receiver. Acoustic tags can also record water temperature, depth and swimming speed. These tags are used most frequently at the Neptune Islands in Great White Shark tagging projects.
Photo: Great White with Acoustic tag near the dorsal fin, photographed by Adventure Bay Charters at Neptune Islands.
Satellite tracking tags send a signal every time the sharks fin breaks the waters’ surface and the transmitter can send the data straight to the satellite receiver. These tags are attached to the dorsal fin of a shark while the shark is held beside the boat. The shark can be followed for the life of the tag battery.
Photo: Satellite tag. Credit http://www.himb.hawaii.edu/ReefPredator/Tools.htm
A second type of Satellite tag is called a Pop up Satellite Archival tag (PSAT) which collects data and stores it within the device. The tag detaches from the animal after a set period of time and floats to the surface, where it then transmits all of its data to a satellite, or the researcher comes along and collects it. This tag can record date, time, swim depth, water temperature, body temperature, energy expenditure and location. These tags are attached to the dorsal fin via the researcher positioning himself so he can reach a long stick to the shark and spear the tag anchor into the skin. This technique is not painful for the animal – all they feel at the most, is a prick, just like you would when getting a needle at the doctors!
Photo: Great White with Acoustic tag at the front & PSAT at the back. Credit http://stanford.io/2qpLwLa
Other types of tags used on marine animals
This tag emits a continuous pulse that can be picked up by a receiver if close enough. The researcher has to follow the pulse in order to follow the animal. These tags are often used in combination with other tags (such as acoustic tags) to allow researchers to find them again.
Photo: Acoustic tag fitted to large catfish. Credit http://bit.ly/2rWQII7
Short term archival tag
This tag has a suction cup which sticks onto the animals back and lasts approximately 24 hours, before it detaches and floats to the surface for the researcher to come along and retrieve. It has accelerometers for understanding dive depth/pitch/roll, stomach temperature sensors, records location, uses jaw based accelerometers/magnetic triggers to identify when the animal is eating, and records sounds. The tag is attached via a long stick (with the tag on the end) and firmly ‘poking’ the animal with it, suctioning the tag to its back. Often used on whales.
Photo: Archival tag. Credit http://bit.ly/2rFAmXp
Great White Shark Tagging at the Neptune Islands
At the Neptune Islands, researchers come to the island regularly to tag sharks and collect data on the various projects that are underway. Previous tagging research has been published in multiple scientific journals, a few of which I will list below.
“Movements and swimming behaviour of white sharks (Carcharodon carcharias) in Australian waters”. By Barry Bruce and colleagues, published in 2006.
- Tags used: Satellite, Acoustic & Number ID tags
- This project showed us that Great White Sharks move very large distances (sometimes from South Australia, all the way to New Zealand), and move into open oceans and across deep ocean basins. However, most movements of this shark were in shelf waters (in area of less than 100m deep, sometimes in water less then 5m deep!). One shark showed changes in swimming behaviour between different habitats, suggesting rapid switching of hunting strategies for different prey types in these habitats.
- How is this information useful in the bigger picture? By looking at the consistency of paths taken by the GWS in Australian waters, we can suggest that they are following common swimming routes in some places. Therefore by identifying such areas we may be able to assist in reducing interactions with fishing operations and therefore reduce the amount of sharks caught accidentally by fishermen.
“The effects of shark cage-diving operations on the behaviour and movements of white sharks, Carcharodon carcharias, at the Neptune Islands, South Australia.”By Barry Bruce and colleagues, published in 2013.
- Tags used: Acoustic
- After the amount of shark cage diving doubled at the Neptune Islands, shark numbers reported by tour operators increased. They also found increases in residency periods, changes in swimming patterns within the water column, and changes in habitat use.
- Results suggest that cage-diving operations can lead to long-term changes in site-specific behaviour. This information can be used when looking at conservation models and managing the industry.
“The effects of cage-diving activities on the fine-scale swimming behaviour and space use of white sharks.” By Charlie Huveneers and colleagues published in 2013.
- Tags used: Acoustic on 21 sharks
- This project found that the presence of shark cage diving operators influences fine scale 3D spatial distribution and rate of movement in Great White Sharks. The sharks spent majority of their time in close proximity to the boats. Individual variation between sharks showed some spent more time near boats than others, highlighting the complexity of relationships between cage diving and effects on sharks. More work is needed to assess whether the observed behavioural changes would affect the sharks in a negative, positive or neutral way.
- Current project by Dr. Huveneers and colleagues adds on to this study: They plan to look at whether effects are positive, negative or neutral on sharks at an individual or population level. Overall aim is to understand the behaviour of white sharks at the Neptune Islands in relation to natural predation and the cage diving industry. For more information about this, head to http://bit.ly/2s1GzsX
Other previous marine animal tagging projects
Previous tagging projects on other animal species have collected data that has been invaluable to the science and conservation of animals in multiple ecosystems across the world.
Archival tags have been used to track migrations of juvenile Southern Bluefin Tuna from the Great Australian Bight to the Indian Ocean. Data collected includes diving patterns and feeding events.
Photo: Daily diving/feeding behaviour of Southern Bluefin Tuna during 11 months at sea. Colours indicate water temperatures at different depths and black circles indicate a feeding event. Credit CSIRO Australia.
Pop up Satellite Archival Tag
These tags have been used on turtles to determine how accidental capture via fishing hooks can affect the health of the animal. Turtles that have been accidentally caught via a long-line have been tagged, released and data gathered once the tag has detached and re-surfaced. This information shows us how turtles respond after being caught accidentally by fishermen; providing data on the long term movement patterns and movement within their habitats, and mortality rates.
Graph: Tracking movements of an Olive Ridley Turtle after being caught on a commercial longline. Credit http://bit.ly/2rFNDPp
These tags have been used in the Pacific Ocean Shelf Tracking (POST) project to study the life history of salmon and other tagged marine animals. Multiple receivers have been placed along the continental shelf and upstream in several rivers to monitor the movements of these marine animals along the shelf. The data acquired form this project can be used to create management policies for fisheries, and add to the understanding of conservation of other marine animals.
Picture: POST acoustic receiver locations as of 2010. Credit POST.
- Hazen, E.L., Maxwell, S.M., Bailey, H., Bograd, S.J., Hamann, M., Gaspar, P., Godley, B.J. and Shillinger, G.L., 2012. Ontogeny in marine tagging and tracking science: technologies and data gaps. Marine Ecology Progress Series, 457, pp.221-240.
- Kenward, R.E., 2000. A manual for wildlife radio tagging. Academic Press.
- Macfarlane, N.B.W., 2015. Tagging wild cetaceans: investigating the balance between more and less invasive techniques (Doctoral dissertation, Massachusetts Institute of Technology).
- McFarlane, G.A., Wydoski, R.S. and Prince, E.D., 1990. External tags and marks. In Historical review of the development of external tags and marks. Amer. Fish. Soc. Symp (Vol. 7, pp. 9-29).
- Rutz, C. and Hays, G.C., 2009. New frontiers in biologging science. Biology Letters, 5 289-292; doi:1098/rsbl.2009.0089.
- Swimmer, Y., Brill, R. and Musyl, M., 2002. Use of pop-up satellite archival tags to quantify mortality of marine turtles incidentally captured in longline fishing gear. Marine Turtle Newsletter, 97, pp.3-7.
- Websites visited 13th may 2017: http://bit.ly/2qlL952 and http://bit.ly/2qVlin8
About the author:
Sarah Hayes is an ecologist and conservationist who has previously done research on bees and monkeys. She is now working with our Great White Sharks and Australian Sea Lions.