How Do Fish Tracking Devices Work?

Over the years, scientists have been studying migration habits for fish. Until recently, tracking a fish in water was an enormously difficult task. However, with GPS tracking, they have been able to do away with guesswork and can reliably track this creature in water and even extrapolate data on their habits. There are three tags used to track fish movement in water.

Passive Integrated Transponder (PIT) Tags.

These are glass-encapsulated tags RFID (Radio Frequency Identification) devices that have integrated circuit chips. They do not have an energy source hence the name passive. Each tag has a unique alphanumeric code to avoid duplication of tags. The tag is loaded in a syringe and is injected into an open space in the fish’s chest cavity. They only become active after being energized by an electromagnetic field. This field is generated by low-frequency waves produced by an antenna attached to a transceiver. The antenna is quite small therefore the detection range is also relatively small. The short detection range makes it hard to track fish when passing through dams and turbines. For adequacy, the number of fish fitted with these tags has to be about 200,000 fish.

Radio Tags.

These tags convey a radio-frequency signal that can be detected through a structure of one or more antennas and transceivers. These tags are usually surgically inserted into a fish, and they function more or less like conventional transmitters but at different frequencies. Antennas and receivers are used to sense typical transmission signals. Radio tags can be used to track the fish habits through dams, reservoirs. They can test for specific route survival, survival and delay and travel times. The signal receiver equipment are programmed to scan for a specified period then move on to the following frequency of concern. However, some scan all the frequencies simultaneously. Above the water surface, receivers can only detect signals up to 30 feet in depth. Under water antennas can track fish under 30 feet depth.

Acoustic Tags.

They use sound waves to pass information from a transmitter via a hydrophone to the receiver. They track fish in three dimension i.e. (x, y and z axis). They tie a signature to a programmed code hence identifying the fish. The transmitted signal can spread for up to 1 km in fresh water. The sound signal comes at a specified time interval. The signals are preset for strength to improve scope and clarity. A collection of receivers allows one to track a fish over a very long distance. The position of the fish in 3D can be determined by getting the arrival time of sound at each hydrophone.

GPS tracking tags can now be used to study distribution, behavior, temperature and migration of fish. These tags are able to track distributions vertically and even horizontally. They can accurately help track fish and give precise locations. This information will aid in construction of safe and efficient structures for fish to pass by. However, no single tag is efficient on its own. For high efficiency, the tags are used in a combined state to address all requirements.