PAT Tags

How Do PAT tags Work?

Popup archival tags (PAT tags) collect and store the depth, temperature and light levels of the sharks' surroundings every minute for the entire length of time they are attached to the shark.  These tags store this information in a memory chip, then at a pre-programmed date and time stop data collection and automatically free themselves from the shark and float to the surface. Once the PAT tag's antenna breaks the surface of the ocean it immediately starts sending transmissions containing a summary of the collected data to the Argos instruments mounted on polar-orbiting satellites. Since these tags are capable of relaying the stored data to the research team without being recovered, they increase the likelihood and ease of obtaining the data. However, in the event that one of the tags is actually recovered, we can download the entire data set that was collected by the tag and gain a lot more detailed information about the shark's movement during the time period.

The approximate latitude and longitude of the sharks' whereabouts each day is calculated using the light level data collected by the PAT tag. The light level data provides a way to determine the sunrise and sunset times for each day and this information is translated via a mathematical geo-location formula into an estimate of the shark's position on the globe. Using the daily positions of the shark we can track its overall movements between the starting and ending position over the course of time the tag was attached.

What Does the Data Tell Us?

Researchers are attaching a PAT tag to a white shark

The tracks that we will reconstruct with the information sent by the PAT tags will allow us to know where the sharks went during the time the instruments were attached to them. One of the main questions we hope to answer with this information is whether the sharks move out of the protected South African waters into other locations where they are not protected. In addition, we will obtain detailed daily information on the depths and temperatures the sharks move through during each day. This will allowing us to reconstruct the movements of sharks in three dimensions and hopefully find more about the relationship between these parameters and the shark's movements. Among other things we will learn how white shark's behavior changes during the day, how often and for how long they dive, the maximum depth sharks reach during dives, and what temperatures and depths sharks prefer. All of this information will give us insight into the ecology and behavior of great white sharks, two knowledge areas where a lot of questions are still left unanswered. 

How are PAT Tags Attached to Great White Sharks?

Above: A PAT tag is attached to the tagging pole ready to be attached to a shark

Pop-up archival tags are approximately 17 centimeters in length, with a float and antenna on one end. The antenna is used to transmit the data to satellites overhead, after the tag has automatically released from the shark. The other end of the PAT tag is united with a monofilament leader to a plastic dart that has barbs and which is used to attach the tag to the shark. In the field, the sharks are lured to the sea surface from a boat, using a piece of bait tied to a rope. Once the shark comes to the bait, this is pulled closer to the boat, and a member of the research team attaches the PAT tag to the back of the sharks using a modified hand harpoon or tagging pole.  The sharks are not harmed by the attachment of the dart which is only about one inch long, and at most they feel only a pinch; in many cases the sharks do not show any type of reaction and seem not to notice the small dart was inserted on their backs alongside their dorsal fins.

Summary of PAT tags attached to Great White Sharks

This is a close up of a PAT tag on the back of a shark.  The black arrow points to the PAT tag

During the first trip to South Africa in August 2002, a total of 3 PAT tags were attached to sharks in Gansbaai and one in Mossel Bay. A total of 2 male and 2 female sharks were tagged, ranging from 190 cm to 350 cm in size. Following this successful trip, the research team continued making progress in April of 2003, when they successfully tagged an additional 8 sharks with PAT tags in Gansbaai and 2 in Struisbaai. During this trip 3 male and 4 female sharks were tagged, with the additional 3 sharks not sexed. The sizes of these 10 sharks ranged from 200 cm to 400 cm.  A month later, during May 2003, 2 more sharks, a male and a female, were tagged with PAT tags in Mossel Bay. During the most recent trip in November 2003, the research team again successfully attached an additional 9 PAT tags onto sharks.  This time they tagged a total of 6 female sharks, 380 to 420 cm in size and 3 male sharks, 260 cm to 300 cm in size.

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