Tagging is the most common form of tracking sharks in the ocean. Tags are more affordable and accessible than satellite devices, they are easily visible and are relatively reliable. This process begins with catching a shark safely and responsibly. The animal needs to be restrained using as little force as possible to avoid trauma, exhaustion and subsequent death. The most common method, favoured by scientists, continues to be gill nets, which are characterised by a fine mesh for smaller sharks and slightly larger mesh for the bigger species. It is imperative that these nets are used properly, as they can prove fatal to the shark otherwise.
The tag needs to be the right size for the shark too. Large, heavy tags will harm smaller sharks or juveniles, and an incorrectly applied tag can fall off (generating incorrect data) or even kill the animal.
The most popular form of tag is the one that is administered by the use of a dart. This dart is placed in the base of the dorsal fin with a long cord, which has all of the capture information printed on it and is usually brightly coloured for easily identification. In addition, it should have the contact details of the person who originally caught and tagged the animal. Should someone catch and kill one of these tagged sharks, it is requested that they call the contact number and advise the person of this event in order to maintain accuracy in the research.
Some sharks are far too large or aggressive to be tagged without sending into a panicked frenzy or endangering the lives of the researchers. In these cases, Casey darts or a pole with a tag hooked onto the end of it is used. These hooks are then used to insert the tag into the base of the dorsal fin from a safe distance. This reduces the amount of struggling that the shark has to endure and results in a calmer, healthier specimen, suitable for re-release.
Should a fisherman catch a tagged shark, which is sometimes visible even under the water as a result of the neon colour of the tag’s cord, he would do well to record the following details and then report them back to the contact person on the tag (if at all possible, the fisherman should then release the shark):
1.Tag number (leave the tag in the shark if it is strong and beable enough to survive release)
2.Date of capture
4.Specs (length, weight)
5.Condition of the animal when released
7.Location of capture
8.Method used (nets, trawl, etc…)
11.Pictures (if possible)
If the shark was caught and killed, the same information would be necessary. However, the captor would then be advised to remove the tag for return to the original captor and to provide his own name and address for a reward.
For more information please view: https://www.hawaii.edu