Like other highly migratory sharks, tiger sharks (Galeocerdo cuvier) often cross international boundaries. Scientists now know exactly where they like to go in the Gulf of Mexico.
Dr Matt Ajemian, assistant research professor at Florida Atlantic University’s Harbor Branch Oceanographic Institute, and a team of scientists fitted 56 tiger sharks with Smart Position and temperature transmitting tags between 2010 – following the Deepwater Horizon Oil Spill – and 2018 – spanning shelf waters from south Texas to south Florida.
The tags transmitted whenever the fin-mounted tags broke the sea surface, with orbiting satellites estimating shark positions based on these transmissions. Ajemian also analysed overlap of core habitats among individuals relative to large features like oil and gas platforms and natural banks.
“While all life stages of tiger sharks are known to occur in the Gulf of Mexico, detailed habitat use has never been quantified,” said Ajemian. “This is rather striking as this marine system faces numerous manmade stressors, complex tri-national management, and indications of size reductions in recreational landings for large sharks.”
By simultaneously tracking many males and females of varying ages within the same region, the researchers observed sex and size-specific differences in distribution and movement, as well as associations with large-scale habitat features.
During cooler months, female sharks visited regions designated Habitat Areas of Particular Concern. These include places like the Flower Garden Banks National Marine Sanctuary. Additionally, shark core regions intersected with 2,504 oil and gas platforms.
Adult sharks moved more frequently and used off-shelf deeper habitats more often than juvenile sharks, particularly during autumn and winter. Furthermore, females moved more often than males when accounting for size.
Photo credit: Albert Kok, CC by 3.0