This is Adelaide, a mature female tiger shark (Galeocerdo cuvier) tagged using a satellite tag in the Ningaloo Reef off Western Australia on April 27, 2015 (Ocearch.org, 2015). She journeyed 378.929 miles over the next month until her last transmission on June 6th, 2015 (Ocearch.org, 2015).
Satellite tag technology has been successfully used to study several marine animals including sharks, whales, dolphins, sea turtles, groupers and has even been used on numerous terrestrial animals as well. In this post we will fill follow Adelaide’s journey and explore the development of satellite tag technology for the use of marine animal study and how the use of this technology is shaping shark research and conservation.
Adelaide’s first transmission is pinged on May 3, 2015 at 5:29 PM, just off the North of Coral Bay, Australia.
The tagging of sharks for scientific study first began in 1942, long before the development of satellite tag technology, when disc tags were wired through the dorsal fin by drilling a small hole using an awl (Stevens, 1999).
Not only did the disc tags require the recapture of the tagged shark to record its location, but they also had a 50% shed rate, which meant for every 100 sharks tagged 50 would lose their tags before recapture. These short comings of the disc tags led to the first use of internal tag placement (Stevens, 1999).
These internal tags had very high retention rate, but very low reporting rates because they were only found during gutting and processing unless accompanied by an external tag (Stevens, 1999).
Adelaide’s second transmission ping came on May 4, 2015 at 6:29 PM, just South of Coral Bay, Australia.
Satellite tags were first developed for shark research in the early-to-mid 1990’s when researchers tagged three blue sharks (Prionace glauca). These early satellite tags transmitted positional data for one month. This was the first time that sharks did not require recapture to acquire information from the tags (Stevens, 1999).
Satellite tags are still the only transmitting tags that allow researchers to get information from the tag without recapture of the animal (Pinniped Ecology Applied Laboratory, 2011). They do so by utilizing the Argos satellite based system to collect, process, and disseminate environmental data by geographically locating the source of data anywhere in the world utilizing the Doppler effect (Morelle, 2007).
Adelaide’s third transmission came on May 6, 2015 at 1:06 PM, further out in the Indian Ocean, off the western coast of Australia.
Satellite tags help researchers glimpse into the lives of sharks in a number of ways. These tags allow data to be gathered on :
- Daily and long term movements
- Physical oceanographic properties sharks encounter during these movements
- Evaluation of depth and temperature preferences
- Catch and release survival rates (Block, Dewar, Farwell, & Prince, 1998).
Adelaide’s fourth transmission came later the same day, May 6, 2015 at 7:31 PM, further south of her last position in Indian Ocean, off the western coast of Australia.
Today there are two types of satellite tags shark researchers can use in their studies.
- Pop-up satellite archival tags (PSAT tags) OR
- Satellite-link transmitters (SAT tags) (Hammerschlag, Gallagher, & Lazarre, 2011)
Both tags are comprised of several components
- A data logging section
- A release section
- A float
- An antenna which sends data via electromagnetic pulse that is picked up via satellite and decoded (Pinniped Ecology Applied Research Laboratory, 2011)
Adelaide’s fifth transmission came on May 7, 2015 at 6:43 PM, just Southwest of Coral Bay, Australia.
Pop-up satellite archival tags or PSAT tags are typically applied from a boat using a tagging lance and requires the tag to be embedded in the sharks’ skin with an anchor (Hammerschlag, et al., 2011).
This method of tagging is highly conductive to tag shedding and premature tag pop-off. Approximately 66% of studies see premature tag pop-off from this method (Hammerschlag, et al., 2011).
Because of this, PSAT tags are normally used in short term studies, usually 30, 60, or 90 days, and are never deployed for more than a year (Hammerschlag, et al., 2011).
Adelaide’s sixth transmission came several days later on May 16, 2015 at 1:31 AM, just Southwest of Coral Bay, Australia.
Satellite-linked transmitters or SAT tags are less conductive to shedding than PSAT tags and are designed to transmit for as long as the tag is attached and the battery life permits. Because these tags have a lower shedding potential, they are usually used in long term studies that can last longer than a year (Hammerschlag, et al., 2011).
A subset of SAT tags are Smart Positioning and Temperature tags or SPOT tags. These are the most advanced satellite tags currently on the market in marine animal science, recording data such as temperature, depth, and salinity. These tags constantly transmit information back to the satellite and thus are perfect for animals which live close to the surface of the water such as sharks, turtles, and dolphins (Hammerschlag, et al., 2011).
Adelaide’s seventh transmission came on May 21, 2015 at 9:04 AM, just South of Coral Bay, Australia.
A limitation of both PSAT and SAT tags are their failure rates. Nearly 10% of tags deployed in all studies fail (Hammerschlag, et al., 2011).
Constant advances in technology are allowing for these failure rates to decrease more rapidly.
- Between 1984 to 2006 in 21 studies, the failure rate per study was 13.5%.
- From 2007 to 2010 in 30 studies the failure rate fell to 7.2% per study (Hammerschlag, et al., 2011)
In long term studies it has been found that bio-fouling from organisms like algae and barnacles are the the cause of most failures (Pinniped Ecology Applied Research Laboratory, 2011).
Adelaide’s eighth transmission came on May 22, 2015 at 5:17 PM, inside Coral Bay, Australia.
Another limit of satellite tags is their ability to have physiological changes on their host.
Anchors for the tags often remain embedded near the sharks’ dorsal fin long after the tag has popped off, providing an attachment site for parasites by damaging the rough dermal denticles that cover their skin and normally keep parasites from attaching (Hammerschlag, et al., 2011).
It has also been suggested that some species may show a change in swimming efficiency due to the hydrodynamic drag caused by the tag. However results have been varied (Kerstetter, Polovina, & Graves, 2004; Hammerschlag, et al., 2011).
Adelaide’s ninth transmission came later the same day, May 22, 2015 at 9:32 PM, still within Coral Bay, Australia.
Satellite tracking tags have allowed for the collection of behavioral data of sharks’ movements in their natural environment over the last 30 years. This data has given researchers the tools they need to transform fisheries management science (Block, et al., 1998; Hammerschlag, et al., 2011).
Now with better understanding of how sharks migrate with prey seasonal availability, to mating grounds, move up and down throughout the water column, etc, researchers are now able to focus their conservation efforts more effectively than ever before (Block, et al., 1998; Hammerschlag, et al., 2011; Ocearch.org, 2015).
One World One Ocean. (2012, March 5). Shark Satellite Tagging – Berry Islands, Bahamas [Video File]. Retrieved from https://www.youtube.com/watch?v=gJfnhokghjw
Adelaide’s final transmission came several days later on June 6, 2015 at 12:14 PM, near her first transmission ping, just North of Coral Bay, Australia.
The amount of data we have been able to collect over the last 30 years since the introduction of SAT technology into shark research has been incredible. Personally, I am excited to see what the future holds for this technology, and what secrets sharks will reveal to us in the coming years.
Thanks for sharing in Adelaide’s journey! Be sure to check out Ocearch.org to track in real time sharks around the world.
Featured Image Source
Ocearch.org (2017). Adelaide Tracking Map [Screen Capture] Retrieved from http://www.ocearch.org/profile/adelaide/
Block, B. A., Dewar, H., Farwell, C., & Prince, E. D. (1998). A new satellite technology for tracking the movements of Atlantic bluefin tuna. Proceedings of the National Academy of Sciences, 95(16), 9384-9389.
Hammerschlag, N., Gallagher, A. J., & Lazarre, D. M. (2011). A review of shark satellite tagging studies. Journal of Experimental Marine Biology and Ecology, 398(1), 1-8.
Kerstetter, D. W., Polovina, J., & Graves, J. E. (2004). Evidence of shark predation and scavenging on fishes equipped with pop-up satellite archival tags. Fishery Bulletin, 102(4), 750-756.
Morelle, R. (2007, June 07). Technology | Argos: Keeping track of the planet. Retrieved June 19, 2017, from http://news.bbc.co.uk/2/hi/science/nature/6701221.stm
Ocearch.org (2015) Adeliade. Retrieved February 11, 2017 from http://www.ocearch.org/profile/adelaide
Pinniped Ecology Applied Research Laboratory. (2011). What Is Telemetry? Retrieved February 11, 2017, from http://sealtag.org/TagTypes.html
Stevens, J. D. (1999). Shark tagging: a brief history of methods. Fish Movement and Migration, 65-68.