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Use of ultrasonic transmitters implanted in fish, in conjunction with arrays of automated, submerged acoustic receivers, has increased the capacity to continuously monitor activity patterns and movement dynamics of organisms, particularly fish. This technology permits remote monitoring of fish in the natural environment, and alleviates the need to continuously track each tagged individual. In this project, we are using a series of acoustic telemetry receivers and transmitters produced by Vemco.
Transmitters, or "tags", emit a series of pings with unique ID codes. The tags are cylindrical in shape and come in a range of sizes. In this study, the tag sizes range from 6-13 mm diameter with smaller tags typically used for smaller fishes. Battery life depends on the tag size, with the smallest tags used in this study having a life of ~250 days (for juvenile snapper) and larger tags (e.g., for snook) lasting over 800. The tags are waterproof with electronics and battery sealed in epoxy. The ‘ping’ rate, at which the transmitter sends out its signal, is set at ~2 minute intervals.
Each transmitter is implanted in an individual fish during a quick and painless, fully anesthetized surgery. Fish are collected either by hook-and-line or fish traps. They are immediately placed in coolers filled with clean, cool, aerated water. With a curved scalpel, a small lengthwise incision is made in ventral part of the fish (its stomach) halfway between the pectoral and dorsal fins. The transmitter is carefully inserted into the incised area, so that the transmitter is aligned parallel to the body. Using a C-curved needle with an attached dissolvable suture, two stitches are made to close the incision. The fish is released in the cooler, and allowed to recover for a minimum of 30 minutes. Once the fish is swimming normally, it is then carefully released at its capture location. (The Abaco Surgery page has more detailed photos and a there is also a video of implanting a transmitter.)
Surgery to implant a transmitter
Vemco VR2 receivers, deployed along the length of the river, detect signals from the tags implanted in fishes. These receivers are submersible devices capable of identifying all Vemco tags. Every time a fish with an implanted transmitter passes a receiver, the unique code of that tag/transmitter (i.e. the fish) is recorded. Receivers are anchored to the bottom or attached to docks and/or pilings. Between river mile 0 (at the Inlet) and river mile 8 (at the border of Jonathan Dickenson State Park), there are currently an array of 24+ receivers deployed (see map). Additionally, we recently have added three receivers within the park area. Data from the receivers are downloaded monthly and immediately uploaded to the web page.
Through the Adopt a Fish, Adopt a School program, anyone can adopt their own fish or purchase a receiver to place in front of their dock. Contact Craig Layman for more information on adopting a fish.