How JSATS Works
The JSATS acoustic transmitters contain a transducer that intermittently produces signals by inducing high-frequency (416.7-kHz) vibrations in the water. These vibrations, or signals, are received by a stationary or mobile hydrophone submerged in the water. The vibrations are converted to electrical impulses that are sent to the receiver, which identifies the signals as a unique tag code and stores them to memory along with the hydrophone identification, time and date of detection, and environmental variables such as pressure and temperature. Data from a single stationary hydrophone allow researchers to determine if and when a specific individual fish passed the hydrophone location. Multiple stationary hydrophones arranged along transects (e.g., across a river channel) are referred to as arrays; the arrays detect whether or not a tagged individual passes a specific site. These types of arrays are commonly used in large rivers, lakes, reservoirs, and estuary and near-shore ocean environments. Three-dimensional hydrophone arrays can be deployed to not only detect the presence or absence of a tagged individual but also provide three-dimensional vectors (range, bearing, and depth) of the individual’s movement. Three-dimensional arrays are frequently used around dams to assess route-specific dam passage behavior. In addition, real-time, three-dimensional movement vectors can be obtained by tracking tagged individuals with a vessel-mounted hydrophone, referred to as mobile tracking - a useful tool for monitoring tagged individuals in lakes, reservoirs, or between stationary arrays in large rivers or estuaries.