Types of tags

4/10/2017

A: A pop-up satellite archival tag on a pole used to attach it to a fish. Pop-up tags release from the animal, pop to the surface, and send stored data to a satellite. B: Two small archival tags. C: A pop-up satellite tag rigged to a shark harness. D: Small plastic tags, once the mainstay of fish tagging, are still handy for some research. Photo: NOAA.

At TFUI, we are committed in not only introducing you to diverse species of sharks, skates, rays and chimaeras but also highlighting the scientists who study them. This week, we want to highlight one of the more popular aspects of #sharkscience: tagging. In this blog post, we want to discuss the different types of tags that can be put on sharks (we’ll focus on #flatshark tagging later on in the week, don’t worry).

Many research projects are focused on tracking sharks and their relatives. The objective of this line of research is collecting data in regards to habitat and migration patterns (amongst other abiotic factors) to help support the conservation of certain species. This kind of data can be collected through several types of tags.

The cheapest types of tags are thin, spaghetti-looking tags that usually have a unique number/color on the tag, along with information to contact the tagging program if the animal is caught or if the tag is found. These tags (like others) have a dart-like tip that is usually driven into the back of the animal, near their first dorsal fin, in a trailing position so it doesn’t hinder the animal’s swimming. Other tags, like satellite tags, are usually mounted to the shark’s first dorsal fin. NOAA does not recommend tagging sharks less than 3' in length with dart tags.

When an animal is caught, researchers jot down information such as the date, the location the animal was caught, how the animal was caught (gear), the size (sometimes just length, other times length + weight), and the sex of the shark. These spaghetti tags can’t record any (what we call) “high use” data such as constant GPS monitoring, pH, water temperature, etc. However, when the animal is caught again (called “re-capture”), data about its growth rate, migration and age can be compared to the first time it was caught.

Acoustic tags can either be attached to or implanted in the shark, skate or ray. The simplest form of these types of transmitters are the “pingers,” which produces a sound signal specific to each individual tag or receiver. The pinger’s sound can be heard via an underwater microphone, called a hydrophone (usually the lead scientist will know what sound belongs to which animal they are looking for). When TFUI Founder Melissa interned at Bimini Biological Field Station, she helped locate small lemon sharks using a hydrophone and listening for these pinging noises. Once a ping was located, we moved the boat in the direction of the ping until we could see the shark (this is called ‘active listening’). A more advanced acoustic tag can often times provide depth and water temperature, and is encoded in the pings transmitted from the tag.

There is also passive acoustic monitoring, which is the same technology but for longer studies (think months or years). These tags are usually surgically implanted into the animal’s body to ensure the longer retention. Instead of having scientists partake in active listening, these transmitters are detected by receivers placed at various locations on the ocean floor whenever an animal with this type of tag swims by. The unique ID code of the animal is recorded, along with the date and time and any of data it has. These underwater receivers usually have a mooring ball on the surface/subsurface so scientists can easily find them again, as the receivers listen for transmitter pings 24 hours a day, 365 days of the year. We’ll discuss more about the data received from this type of tagging later on in the week.

Another type of tag is a data logger, which stores all of their data in onboard memory and must be recovered from the animal for downloading. These tend to have a long-lasting battery and some are even solar-powered! Depending where this tag is, some can report data on internal body temperature, water temperature, and the animal’s swimming depth and the light intensity at said depth. Data loggers usually provide much larger quantities of data than transmitters, but their recovery is not guaranteed. Think: you are trying to find an individual in a very large ocean... it isn’t easy!

Some electronic tags can combine both data logger and transmitter in a single device. For example, many scientists use Pop-Up Archival Satellite Tags/ Pop-up satellite archival tags (PATs or PSAT) to track movements of large sharks. This type of tag is an archival tag (or data logger) that transmits its data via satellite. How? It can store large volumes of data in its onboard memory and summarize the data for lower-volume transmission to satellites. The great thing about this PATs/PSAT tags are that they don’t have to be physically retrieved like an archival tag for the data to be available to the researcher. But, if recovered, then the full record can be downloaded from memory.

Smart Position or Temperature Transmitting Tag (SPOT tags) are tags usually to the first dorsal fin of the intended animal. These tags can remotely relay information to satellite arrays. These tags utilize radio transmissions and have to get in contact with air to send data—therefore, these tags are best used on sharks known to frequent the surface of the water (i.e. great white sharks) so the fin can be out. Now, these fin-mounted tags may cause fin irritation or fin damage, but there is no evidence (thus far) suggesting that it will impact the survival of sharks.

Other Tags
Some tags can detach at a pre-determined date and float to the surface. At this point, the tag will start transmitting all the data that have been collected to nearby satellites. Others can be implanted in the stomach of the animal to measure the pH before, during, and after digestion.

if you know of any other tags, let us know and we’ll add it!

UPDATE:

We've had lots of people talk about this post (awesome). Turns out, spotted ratfish (Hydrolagus colliei) have been tagged with acoustic tags! Here are some other tags--