One method of studying aquatic animal movement, including behavior and migration, is through the use of acoustic telemetry.  Acoustic telemetry involves the implantation of acoustic transmitters into individual animals or attaching transmitters externally.  The sound signal produced by the transmitters can then be picked up by stationary acoustic receivers (hydrophones or underwater microphones) that are positioned strategically to detect the tags.  SERC maintains arrays of receivers in the Rhode and Patuxent Rivers that we monitor and use to help track species such as cownose rays, blue catfish, and common carp.