The Judas Fish

By Jeffery Robichaud

Invasive Species are a big problem in the United States and throughout much of the world. Here in the Midwest, we have our fair share including the zebra mussel, the bush honeysuckle, and the autumn olive. However none gets more attention than our pal the Asian Carp, perhaps because of their flying feats. Several years ago, I wrote for Greenversations about these problematic Pisces.

They continue to be a nagging invasive in our rivers, as well as in those of our sister Region (5) to the east. Staff routinely spot them when we are out on the Mississippi or Missouri Rivers conducting sampling activities (check out the video below). It almost seems comical, but we have had to amend our Health and Safety plans to add the threat of fish strikes as a potential hazard. Here are our folks on a slooooooowww day.

Our scientists have had lots of discussions on how one might safely and effectively reduce their populations, but apparently scientists in the Land of 10,000 Lakes, have come up with a novel solution: introduction of a Judas Fish. From an article in the Minneapolis Star Tribune, which describes the work of Peter Sorensen, director of the new Minnesota Aquatic Invasive Species Research Center at the University of Minnesota:

They are called “Judas” animals because, as the biblical reference implies, they betray. Sorensen said the lessons learned elsewhere using “Judas” animals to locate and kill unwanted species could be used here to fight Asian Carp. Radio-collared Judas pigs, sheep and goats have been released into the wild, then tracked until they lead officials to difficult-to-find herds of the same unwanted species. This week, he will use Judas fish implanted with tracking devices to locate the common carp in Staring Lake in Eden Prairie. Though carp are dispersed in lakes during the summer, they congregate in the winter, and the Judas fish reveal to researchers exactly where they are. A commercial fisherman then will net the mass of unwanted carp, estimated at about 26,000 fish, which root up vegetation, causing lakes to go turbid. Water quality and fish habitat usually improve after carp are removed. Sorensen started using the method in 2008 as part of his carp research. “It’s been very successful,” he said. “Carp are really social animals – one will always lead you to another.” Sorensen said officials could apply the same method to seek out and destroy Asian carp.

I’m not sure how well this will work in our Big Rivers where we see large populations, but if Carp are indeed a schooling fish this might be one of the most efficient approaches to controlling the species. I checked online and could not find any efforts underway to map populations on Region 7 Big Rivers, an activity which might help in maximizing the efficiency of Judas Fish introduction. If you have seen any hot spots, on the Missouri River, let us know with a comment below. Perhaps if enough interest is expressed, we can start a twitter hash tag campaign to collect lat/longs of Carp hotspots on the river, eventually building a crowd-sourced map. I smell another blog post…or maybe it is just the fish.

Jeffery Robichaud is a second generation EPA scientist who has worked for the Agency since 1998. He currently serves as Deputy Director of EPA Region 7′s Environmental Services Division. Jeff has never incurred the wrath of a flying fish. Perhaps his aversion to meals of aquatic animals is sensed by these cantakerous critters who thus leave him alone

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