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One bazillion carp?
Midwest Region, October 15, 2012
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Instant species confirmation: with most SONAR work, biologists don’t always know exactly what species of fish have just been detected below the water surface, however, these jumping silver carp provided an instant species identification for what we just saw on the computer.
Instant species confirmation: with most SONAR work, biologists don’t always know exactly what species of fish have just been detected below the water surface, however, these jumping silver carp provided an instant species identification for what we just saw on the computer. - Photo Credit: Aaron Parker- USFWS
Screenshot of a typical SONAR computer image. The bright orange/yellow line is the river bottom and the elongated vertical ovals are fish that were detected by the SONAR equipment
Screenshot of a typical SONAR computer image. The bright orange/yellow line is the river bottom and the elongated vertical ovals are fish that were detected by the SONAR equipment - Photo Credit: Dave Glover- SIU

Most folks are probably familiar by now with Asian carp. The videos of hundreds of slimy fish leaping from the river and into boats, whacking innocent bystanders in the head leaves an unforgettable image burned into one’s mind. Those of us who have witnessed this first hand have particularly sour memories. When the carp are jumping out of the water, it seems like there must be millions of them in the river, but how many are really present?

Biologists want an answer to this question, particularly in the Illinois River, where carp abundances are high and there is an aquatic connection to the Great Lakes near Chicago. This question is one that fisheries biologists at Southern Illinois University (SIU) aim to answer using hydroacoustic SONAR equipment. Hydroacoustics are regularly used in fisheries work- typically to assess stocks in open systems such as the oceans or the Great Lakes. The application of the tool in rivers is fairly novel.

Last year, SIU biologists were able to scan the entire main stem of the Illinois River in order to get an estimate of Asian carp abundance. This year, they are scanning selected sections of the Illinois River along with side channels, where Asian carp seem to be plentiful. Carterville Fish and Wildlife Conservation Office  biologists got the chance to assist on some of the field collections during the week of October 15th on the Illinois River. Biologists itook shifts on the river helping SIU collect data while learning about the setup, operation, and capabilities of the hydroacoustic equipment.

The SIU researchers had two computer monitors set up safely inside the cabin of their research vessel where images of the river bottom and fish could be seen in real time as as the boat moved along the river. Fish that are detected by the hydroacoustic SONAR devices show up as elongated, vertical oval shapes on the computer screen. When the first few fish, represented by vertical ovals, were observed on the computer screen it was hard to imagine them as actual fish in the water. However, when large groups of “vertical ovals” were observed on the computer in a small area, the all-too-familiar sight of silver carp jumping into and around the boat followed immediately after. Eventually, the Carterville biologists could tell a few seconds ahead of time when the SIU research boat was going to endure an onslaught of carp just by looking at the computer screen first.

The Carterville FWCO has hydroacoustic equipment on order from the manufacturers and is currently learning the technology from SIU with plans to collaborate with SIU researchers and assist in counting fish and developing the methods needed to count fish in the river. If possible with current technologies, Carterville also has plans to try and get species specific  signals developed for Asian carp. This will involve pond experiments testing different SONAR frequencies on caged Asian carp as well as native species. Asian carp specific signals will help to get more accurate counts and will be helpful in other applications, such as finding and targeting Asian carp for removal in areas near Chicago where fish are in low abundance.


Contact Info: sam finney, 618-997-6869 x17, sam_finney@fws.gov



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