Judas Fish technique closer to use with Asian carp
Sixteen Silver and Bighead carp have been caught in Minnesota since 1996, with the most recent being a Bighead caught September 16 at the mouth of the St. Croix River. While we have no way of knowing for sure, we suspect that these catches are of outlier individuals that are not successfully reproducing. But how can we confirm this is the case and also possibly remove these fish given that traditional methods of netting and electrofishing Asian carp are next to impossible?
Dr. Ratna Ghosal, a post-doctoral researcher working with Professor Peter Sorensen, has spent the last two years developing a technique that could do just this. Dr. Ghosal is building on the Sorensen Lab’s success controlling common carp using the Judas fish technique— a technique in which a few radiotracked individuals are followed as they locate (and thus betray) other members of their group. Sorensen’s Lab, with the help of commercial fishermen, has been able to net and remove up to 80% of the biomass of common carp in lakes in a single day.
Dr. Ghosal is determining if the Judas fish technique might be used with Asian carp in rivers as well. This may sound simple, but it is not. First, Dr. Ghosal needed to determine if Asian carp aggregate like their common carp cousins by conducting several tests on their shoaling behavior. She found out that they do.
Next, she needed to determine if she could enhance the tendency of carp to aggregate by making individuals sexually receptive to attract others. She discovered this was possible using goldfish (pictured) as a model and implanting them with hormones that both drive sexual behavior and cause them to release sex pheromones. Experiments are now starting to extend this work to Asian carp.
Dr. Ghosal has also been working with a veterinarian to determine if Asian carp can be sterilized so that researchers may safely release a radio tracked individual into the wild without the concern that it might reproduce. Initial indications are positive, though the sterilized fish are still being monitored.
What’s next for this technique? More trials need to be conducted using hormones on Asian carp, which she expects to complete by next summer. Dr. Ghosal hopes she will then be able to put the technique to the test in large experimental ponds, using sterile Asian carps that have been implanted with radio tags.