In the world's oceans, large sharks function as top predators, and their abundance and distribution patterns can have cascading effects on the ecosystems they inhabit. Despite a lot of public interest in sharks, scientists still have a lot to learn about sharks’ day-to-day lives in the ocean. Many sharks are pelagic, highly-migratory species and, because of their top predator status, they are necessarily rare. They live long lives, mature slowly and reproduce less than many other marine creatures. These characteristics leave them vulnerable to overfishing, and many shark populations worldwide are in decline. In the Gulf of Mexico, declines of both oceanic and coastal shark populations have been reported.
HRI's Center for Sportfish Science and Conservation (CSSC) has tagged more than 5,000 sharks along the Texas coast to monitor shark populations and help fill information gaps about their lives in the Gulf of Mexico. This citizen science project gets anglers and the public actively involved in collecting important information about sharks, so we can learn more about their distribution, feeding habitats, and movement patterns in the Gulf of Mexico.
In our passive tagging program, which is also our largest, we distribute simple tags to local fishermen to help study coastal sharks. Each tag has a unique ID number, and as sharks are recaptured and reported, scientists can determine patterns in capture locations and seasons to understand migration and habitat use by sharks. The center also outfits sharks with acoustic tags, surgically-implanted internal tags that regularly sends out sound signals. With the help of a network of “listening” receivers placed in coastal inlets, scientists can track the sharks’ movement patterns over multiple years.
These methods of tagging have limitations. With passive tagging scientists only know where a shark was captured and where it was released and acoustic tagging is limited to the extent of the network. But a third, state-of-the-art system of tagging allows scientists to track sharks in real time.
The center has partnered with the Texas State Aquarium and the nonprofit OCEARCH to attach satellite tags to larger species like Hammerhead, Mako and Tiger Sharks. The tag, which is attached to the shark’s fin, pings with a location each time the shark surfaces. This provides swift and accurate information about the shark’s current location, which is uploaded to a digital map so millions of shark fans can follow the shark’s movements online. This work is featured in a special exhibit, "Saving Sharks: Where Science and Sharks Meet” at the Texas State Aquarium in Corpus Christi. The CSSC also partners with local fishermen with experience humanely catching and handling sharks like Eric "Oz" Ozolins to deploy tags.