Field Notes
U.S. Fish & Wildlife Service
Field Notes Entry   
A Glimpse of the World Below
Midwest Region, October 4, 2010
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In the swirling, murky water of the Missouri River life abounds.  The species that live here are well adapted to these harsh environments, but until recently the nature of these big river habitats has remained veiled beneath those turbid waters. 

However, this is beginning to change as advances in science and technology are offering researchers a clearer picture of these aquatic environments. 

The giant leap forward in commercial sonar equipment is one such promising technological advancement.  For the past several years we at Columbia FWCO have used Humminbird® Side Imaging® Sonar on our stern trawl boats, and recently Humminbird® offered Down Imaging® Sonar as a free software upgrade.

Side scanning sonar technology was first developed for use by the US Navy more than fifty years ago, but it wasn’t until recently that this technology became available in a format that most people could use and afford.

Both Side Imaging® and Down Imaging® produce clear, picture like images of the underwater world.  Side Imaging® provides up to 480 feet of coverage side-to-side, while Down Imaging® presents an amazingly detailed view directly below the boat.

Using both of these features together gives us a glimpse of the Missouri River like we’ve never had before: individual tree branches are visible, the composition of the substrate is discernable, and even relatively small ripples in the sand can be seen.

While we are still experimenting with the possibilities of these technologies, we have already found several practical applications. With the sonar units installed on our trawl boats, we have been able to avoid large snags which would have severely damaged or destroyed our nets - in this regard the sonar units have already paid for themselves.

Also, the clear images produced by these sonar units allow us to better understand and classify the aquatic habitats which we are sampling. Additionally, this technology provides us the capability to observe how fish are relating to habitat under varying conditions.

Besides Humminbird®, other companies are offering similar technologies. We have recently purchased a Lowrance® Structure Scan TM sonar, which also shows great promise.

The Missouri River can be a tough and hazardous place to work, but new advancements in sonar are making our jobs a little easier - and saving us money in costly net repairs and net replacement.

While we can’t see through the turbid water with our eyes, we can now “see” the underwater world in surprising detail with our new sonar units. The watery realm of the Missouri River will always be something of a mystery, but with new sonar technology it is a little less mysterious, but in my opinion even more interesting.

Contact Info: Colby Wrasse, 573-234-2132 x30, colby_wrasse@fws.gov
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