A year ago, during our coastal shark study field work off the coast of Boavista, Cabo Verde, West Africa, we caught a female tiger shark. After ensuring she was in good shape and taking a range of measurements, we outfitted her with a satellite transmission tag on her dorsal fin and initially called her #52.
Little did we know that she would break records for her kind. Known scientifically as Galeocerdo cuvier, tiger sharks range widely in tropical and temperate seas, and can reach upwards of 5 meters (16+ feet). Curious and generally unafraid, they will investigate and consume a range of potential prey from Albatross birds learning to take flight, to green turtles and marine mammals, to their standard finfish fare. What tiger sharks are eating in the sites where we have found them is still a mystery.
We have since called her Calema in honor of favored musicians in the region and discovered that she has made an exceptional return journey across the Atlantic from Cabo Verde to Brazil and back. This is a first documented transatlantic return trip for this species. Unfortunately, after 263 days at liberty and over 13,000km traveled, Calema’s satellite tag ceased to transmit her positions in August.
This could have been due to the death of the tag’s battery, biofouling of the tag that can inhibit transmissions, or the animal’s death, most often due to being fished. The Eastern Atlantic is a hotspot for large scale fisheries that notably target sharks. We hope that she is still alive, but if dead, Calema has thankfully provided us with the first proof of a return migration by a tiger shark from West Africa.
She may have also revealed that tiger residency in Cabo Verde may be short-term and tied to reproduction or foraging as pups have not been readily observed. More mysteries to solve while we further identify how to abate threats to sharks in the region’s heavily fished waters.