Promising new developments with Judas fish technology
In efforts to find control options for carp, MAISRC researchers have been exploring how to use the Judas fish technique to locate elusive Asian carps. This technique, in which individual fish are equipped with tracking devices and followed as they shoal with other members of their own species, could ultimately help inform lock and dam operations in the Mississippi River.
MAISRC researchers Dr. Peter Sorensen and Dr. Ratna Ghosal developed this method based on work being done in Australia, and it has since successfully been used in Minnesota to remove and control common carp populations. They have recently described several promising new developments that will improve this detection and management strategy.
- Juvenile silver and bigheaded carps have been found to shoal, indicating that the Judas fish technique has promise to lead biologists to schools of other carps. Ghosal is also looking at ways to use pheromones to enhance the likelihood of shoaling and working to pair this with eDNA techniques to better measure their presence. Silver and bigheaded carps have also been found to shoal together. This behavior may explain why these fish have been found to hybridize.
- In order to use the Judas fish technique with Asian carps, it’s crucial that the fish is reproductively sterilized before it is released and tracked. In the course of developing these sterilization procedures for carps in the lab with veterinarians Amy Kizer and Betty Kramek – who are generously donating their services – Ghosal and Sorensen found that common carp can completely regenerate their reproductive organs and grow around vasectomy clips. This surprising development followed a year of monitoring and suggests that different techniques will need to be developed for Asian carps.
- As one of these possible new techniques, Ghosal and Sorensen are now also working with engineers at Advanced Telemetry Systems to help develop an automated system to inject a Judas fish with a lethal dose of poison using a timer. The implanted device would be triggered after the sterilized fish has led managers to groups of other invasive fish – but before it could regenerate its reproductive organs.
“This incremental progress is showing great promise for locating and blocking these elusive carp. They outsmart sampling gear, nets and traps, so we have to get creative to find solutions for control,” said Ghosal.
In order to test the use of the concept using pheromone-scented Judas fish in the field, researchers recently released radio-tagged common carp implanted with pheromone capsules in Long Lake (a collaboration with the Rice Lake Watershed District and the National Science Foundation) and will be tracking its movement and shoaling behavior. Stay tuned for more updates as this work progresses.