Category: Precision

BioBase Project Propels Jeff Schuckman to Nebraska Game and Parks Employee of the Year!

Lake Yankton, a 332-acre backwater lake on the Nebraska/South Dakota border had a problem. In the summer of 2011, the Missouri River flooded, spilling into the lake a number of undesirable invasive rough fish, including large numbers of carp (silver, bighead, grass, and common), smallmouth buffalo, and gizzard shad. Notorious for stirring up lake bottoms while feeding and spawning — and for overeating zooplankton and aquatic plants — these species degrade water quality and fisheries.  

Overrun by these invasive species, Lake Yankton soon looked like chocolate milk, with a water clarity of only three inches — that’s right, inches, not feet.  So the cavalry was called in to assess the situation and provide a solution. Leading the effort was Nebraska Game and Parks Commission District Fisheries Manager Jeff Schuckman.

Fortunately for Nebraska anglers, this wasn’t Schuckman’s first rodeo. He knew the lake could be rehabilitated with careful application of Rotenone, a common fish-killing chemical. The challenge would be to determine just how much of the chemical was needed, and then purchase and apply just enough to do the job — no more, no less.

Continue reading “BioBase Project Propels Jeff Schuckman to Nebraska Game and Parks Employee of the Year!”

Aquatic Mapping Strategies

Producing professional-quality aquatic maps has never been easier with Lowrance and BioBase mapping technologies, but there are several strategies that can help you optimize your time on the water and produce the best possible map output:

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Lowrance GPS Accuracy: Seeing is believing!

A quick post to demonstrate the precision of Lowrance’s internal WAAS corrected GPS antennae is in a variety of open water environments.  Docks? Boat lifts? Overhanging trees?  No problem.  WAAS correction in North America is explained here.  Have a look at a couple examples in ciBioBase:

GPS Track from a Lowrance HDS on Newport Bay, California overlain onto a bathymetry map created by automated processing of the Lowrance .sl2 log file by ciBioBase.  This trip was used for water volume calculations, bathymetry, and vegetation mapping

GPS tracks and ciBioBase derived bathymetry map in a 3-acre pond in a wooded valley in a metropolitan area of Minnesota, an example of retention pond volume monitoring.

GPS tracks and ciBioBase derived contour map of a 3-acre pond in Illinois for water
volume and aquatic vegetation analysis

GPS tracks around docks and boat lifts and ciBioBase derived contour map on Grand Lake O the Cherokees near Tulsa  Oklahoma.  The satellite even shows data collection in an area where a boat can be moored next to the dock.  That’s close!

Lake Bottom Depth Precision and Accuracy

In an addendum to an earlier post, we continue to evaluate the accuracy and precision of BioBase depth outputs.  Lowrance has been in the depth sounding business since 1957.  They have tight factory calibration standards whereby depth should never be more than 2% different than the actual depth.  Of course then we expect depths to be spot on on hard bottom surfaces where truth can be easily measured.  But what about in mucky bottoms which are common place in many lakes, ponds, backwaters throughout the US and abroad?  With this in mind, in late May of 2012, we traveled to Pool 8 of the Mississippi River near LaCrosse WI to do some testing in a mucky, moderately dense vegetated backwater (Figure 1).  At some point we have to step back and ask, “what is the bottom of a body of water?”

Figure 1.  Vegetation cover and biovolume (% of water column occupied with vegetation) in Pool 8 of the Mississippi R. in LaCrosse WI on 5/29/2012.  Average biovolume was 30% during the survey.

The most difficult aspect of this testing was to get an objective estimate of the true depth.  In other words, where exactly did the plants end and bottom start?  Typically, investigators use a survey rod like that seen in Figure 2 to estimate actual bottom based on where they feel resistance on the survey rod.  Piece of cake over sand.  Not so easy over flocculant silt and muck or vegetative areas.

Figure 2.  Measuring bottom with a survey rod in a mucky Minnesota Lake.  Typically, the survey rod will sink several inches into the bottom before the surveyor feels resistance and judges the depth to the bottom

Many experienced surveyors will tell you that the rod will sink into the muck some distance before you feel resistance.  There is a positive correlation in the distance it sinks and how mucky the bottom is.  So, we went into this investigation expecting deeper rod depths measured than ciBioBase outputs. 

Accurate and precise results in mucky, vegetated bottoms

After 30 points measured with the survey rod, we compared the results with the ciBioBase depths measured in the same location.  We were pleased to see very high precision with a Coefficient of Determination (R^2) of 0.94 and a systematic difference in depth of only 4.9″ (Figure 3).  The depth of 4.9″ was quite possibly the average depth where we first felt resistance of the survey rod.  The upshot here is that ciBioBase depth outputs are highly precise, consistent and accurate even in mucky vegetated bottoms.

Figure 3. Accuracy and precision of ciBioBase depths measured against depths collected with a survey rod in the mucky, vegetated backwaters of Pool 8 of the Mississippi River near LaCrosse, WI.
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