Our research teams use a variety of tags to track the movement of sharks. The type of tag used depends on the research question asked as well as the type of shark that is tagged.
What is a PAT tag?
A PAT tag is a popup archival tag, a convenient tag only about 17cm long, with a float antenna on one end and a dart on the other. It collects and stores water depth, temperature, and light levels of the sharks’ environment. The light levels estimate the location by using light data to calculate longitude from day length, and latitude from the time of sunrise to sunset. The data collected is stored on a microchip, and then on a pre-programmed time and date, they release, float to the surface, and transmit the information to the ARGOS satellite. The tags do not need to be recovered by the scientists to download the data, the satellite transmits the information. However if the tag is recovered, the entire data set can be downloaded and analyzed, giving the researchers much more detail into the sharks lives!
Daisy, our hammerhead shark, was tagged with a PAT tag!
Attaching the tag
In order to attach the tag to the shark, the tag is placed at the end of a hand harpoon. The tag can either be attached by researchers from the boat, by free divers in the water, or using rebreather diving. By diving the researcher can get reasonably close to the shark, and more accurately attach the tag. The most difficult part about attaching the tag is finding the shark. The shark can be found by chumming the water, or going to sites where sharks have been seen recently or frequently. The water is chummed by throwing ground up fish, fish oil, and bait into the water. When the shark is spotted, the bait is pulled closer to the boat where the researchers can attach the tag. The best place to attach the tag to the shark is on their back along the dorsal fin. The one inch dart is then injected, and the shark goes off.
What can be learned?
The data set sent to the researchers will show the sharks’ migration patterns, how deep they dive, for how long, what temperatures they prefer, and much more. With this information countries, governments, researchers, and conservationists can develop better ways to protect these amazing apex creatures! (top)
What are Acoustic Telemetry Tags?
Acoustic telemetry tags are increasingly being used to study the movements of fish and sharks. They can record analyze and store data on depth, temperature, and light levels. The most common place to use these tags is in marine environments such as estuaries, deep sea, and the continental shelf, but it can also be used in rivers, lakes, and dams. These tags are relatively small, about 15 to 150 mm in size, and weighing 1 to 80 grams. The bigger the animal the bigger the tag, and therefore more information can be collected.
There are two main categories for this type of tag, passive telemetry and active telemetry. In both, a transmitter is used to emit the signals, hydrophones are used to convert those signals, and receivers are used to record the signals. The transmitter is the tag itself, which gathers all the data and is attached to the animal. This transmitter sends out a sound signal that easily moves through water. The hydrophone receiver then picks up this signal and converts it into the data the researchers use. In order for the receiver to pick up this information, the tag must be within a certain range.
In passive telemetry the hydrophone is attached to permanent listening stations. These stations are located around islands, in bays, or canyons and typically have a range of 100 to 1000 meters. The advantage of passive telemetry is that information can be collected 24 hours a day, for long periods of time. The disadvantages are if the fish leaves the area, there is no way of knowing where it went, and the exact location of the animal is seen in a 3D type of image.
In active telemetry the hydrophone receiver is attached to the research vessel. The vessel can be as small as a kayak or as big as an oceanic research boat. The transmitter emits a sound pulse that the hydrophone picks up, and the intensity of the pulse indicates how far or close the animal is to the vessel. The downfall to active telemetry is that the data collecting is long and hard, it can only last for as long as the researchers can stay at sea, and if the weather is permitting. However a lot more can be learned from this method such as the animals’ heart rate and tail beat. Scientists are able to track and monitor what the animal is doing at exactly that moment, hence real-time tracking.
How is it attached?
The tag is either attached to the back of the fish, or placed inside its stomach. In order to attach the tag to the back of the animal, it must first be lured close to the research team on the boat. It is then captured and the tag is placed at the base of the dorsal fin using a plastic band or plastic screws. Or it is placed inside its stomach by putting a tag in a prey item that the animal likes to feed on. This method is least stressful for the animal, and considerably safer for the researchers.
What can be learned?A lot can be learned from acoustic tagging. Since real-time tracking can be used researchers can map out the daily life style of the animals. The tracking can also reveal secrets to large-scale fish movement, and fine-scale movements of individuals. In the long run habits and behaviors will emerge, and scientists will be able to effectively conserve and manage the species and their environment. (top)
What is a SPLASH Tag?
A SPLASH tag is a data collecting Argos satellite tag. It is also considered a near-real time satellite tag because the information can be relayed to the scientists instantaneously. Like the SPOT tag, the SPLASH tag comes equipped with an automated battery saving switch. When the sharks’ fin breaks the surface of the water, the switch turns on and sends the signal to the nearest Argos satellite. The signal will be relayed for approximately fifteen minutes, and then switches back off. If there is no satellite to pick up the signal, the signal is lost and the scientists will not get the data for that day. This explains why sometimes sharks can go for days without sending information. The scientists also have the option of limiting the amount of transmissions a day, or allowing the tag to send information only if a satellite will be able to pick it up. SPLASH tags provide where the shark has been in the past twenty-four hours, the position, temperature, and depth of water.
How is it attached?
The SPLASH tag is attached the same way as a SPOT tag. First the shark is lured by using bait and chum. When the shark is lured close enough the team catches the shark using a special double hook. As always there is a veterinarian present at all times, and the least amount of stress would be inflicted to the shark. The tag is attached by drilling holes in the sharks’ dorsal fin, putting plastic bolt through, and securing it with metal nuts and washers. The tag is designed so that after a long period of time it will corrode and fall off. Before being released back into the water the hooks are completely cut off and removed. It will leave a small wound, which will heal within a few weeks time.
What can be Learned?
As with all the other tags, a lot can be learned form tagging sharks. First and foremost the migration route of these animals are of utmost importance in the conservation effort. A lot can also be learned about their feeding habits, behaviors, and habitats. It brings us one step closer to understanding these widely misinterpreted animals! (top)
What is a SPOT Tag?
A SPOT tag is a smart position or temperature transmitting tag. It records temperature, salinity, and depth. SPOT tags are considered near real-time tags because you can gather the data day to day when the sharks’ dorsal fin comes out of the water. Some of the tags are equipped with a switch that will turn off when submerged in the water to conserve the battery life. When the tag is above water the signal is sent to Argos satellites, and is then sent to the researchers and scientists via email. It has a typical life span of about two years, and is fairly expensive and requires large batteries.
How is it attached?
When attaching the tag the sharks’ safety is the most important concern! It is crucial that the least amount of stress and injury be placed on the shark. First the shark must be lured to the boat and into a specially designed shark cradle. When the shark is safely in the cradle, it is lifted out of the water and the researchers begin their work. There is a veterinarian present at all times to ensure the sharks safety, and they pump seawater through its mouth and gills to ensure a constant flow of oxygen. The tag is then attached to the dorsal fin with two plastic screws. Then the cradle is then lowered back into the water, and the shark is free to go.
What can be learned?
Because SPOT tags can send near-real time information, the scientists can put the information straight to good use. The scientists can monitor the sharks’ migration route day to day instead of waiting months and months for the tag to release. This way they can go directly into fighting to protect the areas the sharks frequent! (top)