Closely-tracked sharksFri 12 Oct, 2018
Knowing the geographic position of the sharks can be reassuring for swimmers. But tracking them is also of interest for researchers. Knowledge of the movement of animals and their distribution in space contributes to the understanding of the interactions with their environment, including with other species, and might thus be helpful to adapt conservation actions. Three species of sharks were recently studied by different teams of researchers.
In a bay of St John, US Virgin Islands, no less than 17 young blacktip sharks (Carcharhinus limbatus) were equipped with acoustic tags, small sound-emitting devices that allow the detection of the animals. Following their capture, sharks were placed ventral side up to induce tonic immobility, a sort of hypnotic paralysis, allowing the researchers to implant the transmitter in the body of the animals. The movements were then monitored using 25 fixed acoustic receivers dispersed in the bay. After one year of follow-up, the results show a diel horizontal movement pattern. In other words, sharks do not spend their nights in the same places they spend their days!
In another study in the Bahamas, 14 Caribbean reef sharks (Carcharhinus perezi) received acoustic tags. Two months of follow-up were sufficient to show that males have larger home ranges than females. Finally, around Cuba, three female silky sharks (Carcharhinus falciformis) were equipped with satellite-linked tags, devices allowing a more complete follow-up compared to acoustic tags. The data revealed the preferences of the sharks in terms of habitat: temperature, average depth … They also show a diel movement pattern, vertical this time: sharks spend greater time at depth during the day than at night. These useful data increase the knowledge about the ecology of these three species and might also be used to observe the impact of certain disturbances such as … eco-tourism!
Article submitted by Sophie Labaude
Hueter, R. E., Tyminski, J. P., Pina-Amargós, F., Morris, J. J., Abierno, A. R., Valdés, J. A. A., & Fernández, N. L. (2018). Movements of three female silky sharks (Carcharhinus falciformis) as tracked by satellite-linked tags off the Caribbean coast of Cuba. Bulletin of Marine Science, 94(2), 345–358.
Legare, B., Skomal, G., & DeAngelis, B. (2018). Diel movements of the blacktip shark (Carcharhinus limbatus) in a Caribbean nursery. Environmental Biology of Fishes, 101(6), 1011–1023.
Shipley, O. N., Brownscombe, J. W., Danylchuk, A. J., Cooke, S. J., O’Shea, O. R., & Brooks, E. J. (2018). Fine-scale movement and activity patterns of Caribbean reef sharks (Carcharhinus perezi) in the Bahamas. Environmental Biology of Fishes, 101(7), 1097–1104.