Wednesday, June 26, 2013

Optimal Percent SAV Biovolume? 50% is a Good Start


At Contour Innovations we've long argued the importance of objectively assessing submersed aquatic vegetation (SAV) abundance to better inform management decisions.  Our last blog post discussing a recent controversy over the role of herbicides in indirectly affecting fisheries declines in Wisconsin reinforces why this is so important.  When we talk abundance per se, we need a metric that is quantitative, yet is intuitive.   The percent of the water column taken up by vegetation growth (i.e., percent "biovolume") represents such a metric and is the primary variable that is mapped in ciBioBase.  Zero means no growth (blue).  100% represents growth all the way to the surface (red; Figure 1).
SAV, Aquatic Vegetation map, Lowrance HDS, Surface growing vegetation
Figure 1. SAV Biovolume map (left), boat tracks (red lines), boat location (red dot), and sonar chart of vegetation growing to the lake surface on Orchard Lake, MN.

Zero is undesirable in lake environments where vegetation growth is natural or where an artificial lake is managed for vegetation-dependent fisheries (e.g., largemouth bass or northern pike).  No vegetation growth can also cause and be an effect of water quality impairments as discussed here).  In contrast, 100% is undesirable from an aquatic recreation standpoint because props get tangled up and it's difficult to navigate your boat through surface mats of vegetation (Figure 2).
Figure 2. Aquatic Vegetation (100% Biovolume) growing all the way to the water surface on Orchard Lake, MN and impediments to motorized recreation. 

If no plant growth is bad (0%), but plant growth all the way to the surface (100%) is bad, then good MUST be somewhere in between.  Indeed!  From a Fisheries standpoint, 40-60% average biovolume is good because there is habitat for vegetation-dependent species like largemouth bass, bluegill, northern pike, and indicator species like blackchin shiners that are sensitive to vegetation loss (Figure 3).
Figure 3.  Probability of sampling blackchin shiners as a function of increasing SAV % biovolume  in Square Lake, MN (Adapted from Valley et al. 2010 Hydrobiologia 644:385-399)

From a water quality standpoint, 40-60% biovolume is sufficient to anchor sediments and will promoting better water clarity than if nothing was growing.  Finally, 40-60% biovolume means that most growth is below the depth of your outboard prop and thus you generally won't encounter the situation as seen in Figure 1.

A case study in MN, WI, NC, and FL lakes

CI is currently involved in a collaborative research project where acoustic data with Lowrance HDS was passively collected while conducting point-intercept surveys.  Acoustic data (.sl2 files) were uploaded to ciBioBase and the Biovolume value for each species survey point was extracted from the exported raster grid ("Extract Value From Point" in the Spatial Analyst Toolbox in ArcGIS or see our Point-Intercept on Steroids blog).  Figure 4 displays a wealth of information about the status of plant growth and management in the surveyed lakes.  With on-the-fly data entry for the plant species surveys and uploading of the .sl2 file to ciBioBase, a similar graph could be produced within hours of finishing a survey, and thus facilitating informed and rapid decision making.
Figure 4.  Biovolume at invasive species sample points and native sample points free of invasive species.  Non-vegetated sites are not included in the analysis.  Lakes range from intermediate nutrient levels, Mesotrophic (M), to high nutient levels, eutrophic (E).  Berry, Gibbs, Swan, Wingra, and Round are in WI; Gray's, Gideon's, and St. Alban's Bays are bays of Lake Minnetonka, MN; Waccamaw is NC; Tracy, Kissimmee, Istokpoga are FL lakes.  All MN and WI lakes are infested with Eurasian watermilfoil.  All NC and FL lakes are infested with Hydrilla.  Waccamaw is bog stained and the hydrilla is a recent infestation

Specifically this graph tells us the following:

  1. Invasives grow closer to the surface of lakes than natives and growth seems to be highest in lakes of intermediate productivity (meso-eutrophic)
  2. Natives appear to grow at the 40-60% biovolume level regardless of productivity.
  3. Native growth can be an objective benchmark from which to judge the success of invasive management in non-eradication management regimes.
  4. Aquatic Plant management was successful at bringing down invasive growth to the level of natives in Gray's Bay of Lake Minnetonka, Kissimmee, and Istokpoga
Something as simple as what is displayed in Figure 4 can bring an objective point of reference to the table when discussing the often controversial nature of aquatic plant management.  With data such as these, discussions by various user and management groups can center on the acceptable level of growth to meet Fisheries, Water Quality, and Invasive Species management goals (which we argue can occur at some intermediate level of plant growth).  Without both species AND abundance data, various factions will continue to take up positions with anecdotal evidence that support their prejudices and the discourse will never get to where it needs to be to tackle these important water resource issues.

Tuesday, June 18, 2013

The Wake Up Call to Action for Objective Lake Monitoring and Management

The unexpected consequences of fighting Eurasian Watermilfoil, preventing fish from successfully reproducing?  Response by Contour Innovations’ President Matt Johnson

Recently, freelance journalist and underwater photographer Eric Engbretson published an article entitled 'The unexpected consequences of fighting Eurasian Watermilfoil, preventing fish from successfully reproducing?' on a news service blog sponsored by Fishiding.  The article's focus was Lake Ellwood Wisconsin where Wisconsin DNR Fisheries Biologist Greg Matzke presented evidence of declining Largemouth bass, Northern pike, and bluegill populations and evidence of recurrent reproduction/recruitment failures of these species.  Much of what is presented can be found in a draft WI DNR Fisheries Report.  Matzke speculates that declines in populations of these vegetation-dependent species may be due to a loss of aquatic vegetation over the last 10 years by repeated whole lake treatments.  In the DNR Report Matzke presents spotty, often subjective estimates of aquatic plant abundance which makes it difficult to confidently associate aquatic plant declines due to treatments with declines in fish populations.

It’s often difficult to respond to topics like this because, as a non-biologist and an employee of private company that provides a product for this field, I’m always concerned that my comments would be misconstrued as commercial, driven by my interest to sell products or my failure to understand the biology behind the “whole picture.”  I approach this topic as an outsider that gets to observe the industry and sometimes provide a unique perspective without a specific interest or deep understanding of a particular biological issue.   It is this observation stance that allows me to recognize that this article is a wakeup call regardless of position.

Every opinion, no matter what side of a topic you land on, will go nowhere if we don’t have objective information to make an argument or defend a position.  This is something both government biologists/regulators and aquatic service providers should agree on here.  This report is an opportunity to finally connect all groups within the aquatics field to perform holistic investigations, recognize when there’s a lack of good data, and take steps to acquire critical data.  It’s an opportunity to have the discussion the aquatics field deserves.  Failing to at least put resources towards making the connection between data inadequacy and historical needs from this article is a failure in the structure of the aquatic industry and maybe even society.  Compliance is one thing while a constant quest towards better data-intensive monitoring and management is quite another.

Sometimes this lack of “good data” is a result of a failure of technology to provide the tools required to gather and analyze the information we need, and sometimes it’s for other reasons like budget, human resources, access, and priorities.  I struggle with the paradox that the some people who argue that we need to look at the data before we make decisions on Ellwood are some of the same people I’ve seen resist an objective method that can provide these results.  It doesn’t add up.  Without objective, repeatable aquatic plant assessment methods, the field never moves forward and everyone gets to pick a side and stay there. Consequently, circumstantial evidence and speculations are used to assign a cause and place blame.  This puts the accused on the defensive using lawyer tactics to avoid any accountability.  This gets us nowhere

A way forward . . .

Contour Innovations is already helping to facilitate collaboration between fish monitoring and invasive plant management with fantastic, even unexpected results.  All involved hope the data sharing model grows into the future of monitoring and management.  By using an objective, passively logged and repeatable system of plant abundance and characteristic monitoring, multiple interests are benefiting simultaneously.   Fisheries managers are using quantitative measures of aquatic plant habitats to formulate fisheries management goals, Invasive aquatic plant managers are using these same data sets to evaluate invasive nuisances and are taking measures to address the nuisance while not compromising fish habitat.  This is a different way of thinking proactively instead of reactively and we can’t miss opportunities to highlight the need.  We can claim that the technology is the future, but technology is merely a catalyst for the necessary paradigm shift.

Our position has remained consistent since the Company’s founding, but is more relevant now than ever: That is, prudent management and regulation of lake ecosystems requires that decisions be based on objective, quantitative information about the status and trajectory of the system(s) of interest.  Continued decisions in an information-poor or anecdotal-evidence environment risk situations and blame like those observed on Lake Ellwood.

We haven’t picked a side but the industry and field needs to embrace or seek a more standardized or objective way of measuring aquatic plant abundance data.  I’ve heard a lot of requests for automated speciation data but here we are wishing we had objective abundance data.  There are some “cool” parts of our systems but we started BioBase because it fills a need.  Subjective methods of plant monitoring are already outdated. This has never been more apparent.

Friday, June 7, 2013

Guest Blog: Using ciBioBase to determine sedimentation in the Central Arizona Project canal

by Scott Bryan

The Central Arizona Project (CAP) is a multipurpose water resource development and management project that provides irrigation, municipal and industrial water to much of Arizona.  The primary means of water conveyance is a 336-mile concrete-lined aqueduct that transports water from the Colorado River, on Arizona's western border, across the State to Phoenix, and then southward to the aqueduct terminus near Tucson.  Each year, over 1.5 million acre-feet of water is delivered to our customers.

Since its completion in 1993, the aqueduct system has experienced increasingly severe sedimentation that creates problems within the pumping plants and in the aqueduct itself.  Because the sediments can decrease the flow capacity of the aqueduct, cause damage to pumps and internal systems, and restrict flow through critical filtration units, it is imperative that dredging operations occur periodically.

sedimentation, ciBioBase, water volume, depth, mapping, bathymetry
CAP forebay dredging in 2009
In the past, CAP performed intensive sonar based sediment studies to determine bathymetry and the amount of deposition in the forebay of each of the 13 pumping plants.  The surveys show when and where dredging operations should occur.  These surveys were contracted to outside companies with costs ranging from $40,000 to $120,000 annually.

In 2012, CAP began to use the sonar technology provided by ciBioBase to conduct its own bathymetry surveys in the pumping plant forebays.  Water depths are compared to historical baseline surveys and the volume of sediment in each forebay can easily be calculated.  Annual surveys allow us to compare sedimentation from year-to-year to determine loading rates and critical areas to target sediment removal.  Surveys of all 13 forebays can now be accomplished in three days rather than six months, and when compared to the expensive surveys from the past, are equally as accurate.

ciBioBase, bathymetry, water volume, depth, Lowrance, acoustics, mapping, sonar, sedimentation, dredging
Blue-scale bathymetric map of a CAP forebay.  The light blue contours show an area that is extremely shallow and is in need of sediment removal.

ciBioBase, sedimentation, Lowrance, downscan, sonar, mapping, bathymetry, depth, water volume
Example transect design and resultant bathymetric map coupled with the sonar log viewer.  Notice the detailed image of the forebay's trash racks produced by Lowrance HDS DownScan
This new approach to bathymetric and sedimentation mapping saves time and money, allows us to evaluate results immediately, and makes dredging operations more efficient and timely. 

Scott Bryan is the Senior Biologist for Central Arizona Project (CAP).  After receiving an M.S. in Fisheries Management at South Dakota State University, Scott worked as a research biologist for Arizona Game and Fish for 10 years, then specialized in lake and stream management for seven years at a private consulting firm in Albuquerque.  Scott's current position at CAP includes a broad scope of work, including aquatic and terrestrial vegetation control, fisheries and wildlife management, invasive species research, and water quality monitoring.