This is Sharka Khan, a female oceanic whitetip shark (Carcharhinus longimanus) tagged using a satellite tag in the Caribbean on May 30, 2016 as part of the Guy Harvey Ocean Foundation research. She journeyed 327.23 miles (526.62 km) over the next four months until her last transmission on September 22, 2016 (Guy Harvey Ocean Foundation, 2016).
Sharka Khan’s first transmission is pinged on May 30, 2016, just off the North of the Cayman Islands.
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 Sharka Khan’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.
Sharka Khan’s second transmission is pinged on June 4, 2016 at 11:11pm, due east of her first transmission.
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.
Sharka Khan’s third transmission ping came on June 5, 2016 at 12:29am, in the same area as her second transmission.
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).
Sharka Khan’s fourth transmission ping came on June 6, 2016 at 10:32pm, northeast of the Cayman Islands.
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).
Sharka Khan’s fifth transmission came on June 8, 2016 at 10:03pm, southeast of the Cayman Islands.
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).
Sharka Khan’s sixth transmission came on June 15, 2016 at 12:51pm, further southeast of the Cayman Islands in the Caribbean.
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).
Sharka Khan’s seventh transmission on June 22, 2016 at 3:03pm, in the middle of the Caribbean, southeast of the Cayman Islands.
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)
Sharka Khan’s eighth transmission came on July 1, 2016 at 12:00pm, southeast of the Cayman Islands in the Caribbean.
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).
Sharka Khan’s ninth transmission came several days later on July 11, 2016 at 11:10am, in the Caribbean Sea.
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).
Sharka Khan’s tenth transmission came on the following day on July 12, 2016 at 12:24pm, in the Caribbean Sea.
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).
Sharka Khan’s eleventh transmission came nearly two months later on September 1, 2016 at 11:27pm, to the southeast of the Cayman Islands.
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).
Sharka Khna’s twelfth transmission came on September 4, 2016 at 10:51pm, east of the Cayman Islands.
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
Sharka Khna’s final transmission came on September 22, 2016 at 11:25pm, in the middle of the Caribbean.
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 Sharka Khan’s journey! Remember you can make a difference for marine ecosystems by calling your Congress man or woman and tell them that you care about the quality of our waters! Sharks, rays, and other marine organisms cannot speak or be represented in Congress. They need your voice. Get involved and stand up for sharks.
Featured Image Source
Guy Harvey Ocean Foundation. (2016). Sharka Khan’s transmissions [Digital Image]. Retrieved from http://cnso.nova.edu/sharktracking/
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.
Guy Harvey Ocean Foundation. (2016). Sharka Khan’s transmissions. Retrieved from http://cnso.nova.edu/sharktracking/
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
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.