Acoustic or sonic tags emit sound waves that can be tracked by researchers on ship or shore using a hydrophone. They allow for direct tracking of the movement of a tagged animal. The tag can be embedded in the animal by cutting a small incision in the abdominal cavity, or attached externally using a barb or adhesives.
During the early 2000s, researchers at the Virginia Institute of Marine Science used acoustic tags to gain a better understanding of the movements of juvenile sandbar sharks in Virginia waters. Researchers followed shark activity in Chesapeake Bay using a hydrophone. On the Eastern Shore, they set up listening stations in Wachapreague and Machipongo to record each time a shark with a sonic tag swam by.
VIMS researchers also deployed acoustic tags in Prince William Sound, Alaska, to study the ability of salmon sharks to retain body heat. Salmon sharks use counter-current heat exchangers (retia mirabilia) to keep their body temperature greater than that of the cold waters of their habitat. This allows them to hunt active prey like salmon.
- Juvenile sandbar sharks move large distances in short periods of time, but they tend to stay within their Eastern Shore nursery grounds during the summer and return to the area in subsequent summers.
- Sharks appear to move in the direction of the tidal current.
- Shark locations are correlated with daylight; more sharks were detected by the array during the night and early dawn hours.
Conrath, C.L. 2005. Nursery delineation, movement patterns, and migration of the sandbar shark, Carcharhinus plumbeus, in the Eastern Shore of the Virginia coastal bays and lagoons. Ph.D. Dissertation. College of William and Mary, Williamsburg, Virginia.
Anderson, S.D. and K.J. Goldman, 2001(3). Temperature measurements from salmon sharks, Lamna ditropis, in Alaskan waters. Copeia: p. 794-796.