Where do sharks go? Anglers help provide insight on shark movements

Sharks fill the role of apex predators in the marine ecosystem, but global populations are in decline partly due to overexploitation by the commercial fishing industry and the desire of some misguided fishermen to remove “dangerous” species from the ecosystem. Management of these species is difficult due to their large-scale movements, which often cross multiple state, federal, and even international jurisdictions. Shark population data has traditionally come from fishery surveys that have been limited on spatial and temporal scales, and nearshore shark assemblage data in the Gulf of Mexico (GOM) were limited to federal waters (>20 m-depth). Only in the past decade has this trend begun to change, as more surveys are being conducted in coastal waters. However, these surveys are still infrequent leaving large data gaps regarding movement and habitat use by these important species.

 

Since the 1960s, land-based recreational shark fishing has been a popular sport in Texas and has recently switched from a harvest-based fishery to a catch-tag-release fishery. Additionally, there are no seasonal restrictions on recreational catch and release shark fishing in Texas. These unique circumstances provide an opportunity to consistently collect valuable long-term data along the Texas coast and engage a large number of recreational anglers as citizen scientists that can help with this conservation effort. Data can be provided by these anglers after every fishing trip rather than in the one or two surveys conducted annually by scientists.

 

The Center for Sportfish Science and Conservation (CSSC) works closely with recreational anglers to tag sharks in the Gulf of Mexico. To date, recreational anglers, including participants of the Texas Shark Rodeo and Sharkathon, have tagged an impressive >4,100 sharks! These data are useful in exploring composition and seasonality of shark species. However, some of the most interesting data comes from when sharks are recaptured. Recaptures allow CSSC scientists to explore shark movements along the coast and determine if and when sharks return to their initial tagging location, in addition to growth measurements.

 

Eighty-two recaptures have been reported around the Gulf of Mexico since 2011.

 

To date, 82 recaptures have been reported and not all sharks have stayed in US waters!

 

Most recaptures have occurred in Texas waters where the sharks were initially tagged, suggesting that these sharks stay in the area.

 

A blacktip caught off Padre Island National Seashore in November 2014 was recaptured in Veracruz, Mexico in January 2015, traveling an impressive 580 miles between the initial and recaptured tagging locations, the longest migration we’ve seen thus far.

 

Initial tagging and recapture locations of the blacktip shark recaptured in Mexico. This is the current record for furthest distance traveled between tagging events.

 

Blacktip tagged in 2013 and subsequently recaptured 3 times in 2013.

 

Most sharks are recaptured within the first year after tagging, but a few have been caught after several years at liberty. Two sharks, a sandbar and tiger shark, tagged by recreational anglers were recaptured three years later, which is the current record for the longest time at liberty.

 

Sandbar tagged in 2014 by Grant and recaptured by Donnie in 2017 almost to the date.

 

Some sharks have even been recaptured multiple times! A blacktip tagged in 2013 was recaptured 3 times that year and a great hammerhead tagged in 2016 has been recaptured twice to date. Recaptures are a rare occurrence by themselves, but to be recaptured more than once is an extremely exceptional event!

 

Great Hammerhead tagged by Rocky in 2016.

 

Great Hammerhead recaptured for the second time by Josh.

 

This large scale tagging initiative and valuable data would not be possible without the participation of these dedicated recreational anglers. If you are interested in helping the CSSC team, visit our website for more information on how to get involved!

The Center for Sportfish Science and Conservation is a center at the Harte Research Institute for Gulf of Mexico Studies where Dr. Greg Stunz is also the Endowed Chair for Fisheries and Ocean Health...

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