Argos satellite system helps track porbeagle sharks
Porbeagle shark is a wildlife species which migrates long distances. Monitoring their movements is important to help protect them. Since they are permanently subaquatic, they are located using Argos pop-up satellite archival tags.
The migration of nine porbeagle sharks have been monitored for several months and up to one year by G. Biais of Ifremer, Unité Halieutique Gascogne Sud. During that time, they have covered 5000 to 13000 km, reaching an area about 2000 km from their starting point, in a wide variety of directions – North, South, West. Fished in Europe from the 1930s, the species has declined and is now protected. Knowing its migration is thus useful to develop a greater understanding of porbeagle biology and ecology.
Tracks of the nine tagged porbeagles (Credits Ifremer)
Porbeagle sharks (Lamna nasus) have no need of surfacing to breath, feed or anything. The usual way of retrieving a migratory animal location for wildlife tracking is when the Argos PTT is out of the water, since the signal does not transmit well across a thick layer of water. When animals are always subaquatic, specific beacons, “pop-up satellite archival tags” have been developed to locate them. They register information including light, temperature, pressure, while the tracked animal is moving and up to a pre-programmed time when the tag detaches itself from the animal. Knowing the light intensity and orientation, the temperature of the water and the depth, a location can be estimated. When the tag detaches and thus surfaces, the data are retrieved using Argos satellites wherever this occurs in the oceans. CLS Argos is then processing them to fine-tune the track with the “track & loc” service.
Useful links & references
© Image : Return to sea of a tagged porbeagle (photo G. Biais, Ifremer)
Biais Gerard, Coupeau Yann, Seret Bernard, Calmettes Beatriz, Lopez Remy, Hetherington Stuart, Righton David (2017). Return migration patterns of porbeagle shark ( Lamna nasus ) in the Northeast Atlantic: implications for stock range and structure . Ices Journal Of Marine Science , 74(5), 1268-1276