Guest Blog: understanding growth patterns of invasive Flowering Rush and Eurasian watermilfoil in the Spokane River System.

Tamara Knudson
Limnologist
Spokane Tribal Fisheries
Airway Heights WA, USA

We recently began collection of baseline data on a small reservoir in northeast Washington State to gain a better understanding of the aquatic community and effects of the hydrological system on the flora and fauna. There is little public access and surveys along this stretch of river are limited. Flowering Rush and Eurasian Watermilfoil, both invasive plant species, have been identified in the reservoir, but distribution fluctuates coincident with changing water elevations and flows. Distribution of the plant community in the reservoir is not well understood. Traditional plant survey methods using the rake method are used to collect submerged plants, but the patches need to be located first. Bathymetric maps used previously were limited and we were looking for a good way to locate and map distribution of vegetation throughout the reservoir. Identification of the vegetation patches would allow us to target specific locations for invasive plant monitoring and inform fish surveys. To accomplish this, we used the Lowrance HDS12 with side and down scan capability. We made several tracks throughout the reservoir to maximize coverage and recorded all our movements on the Lowrance unit. The process was fairly simpleā€¦as we drove the boat around the reservoir, we recorded our tracks and saved the files as .sl3 files on the Lowrance unit, and uploaded them to the BioBase website. Once BioBase received the upload, they processed the data and we were then able to obtain bathymetric and vegetation heat maps that included vegetation percent biovolume such as the one shown below.

SpokaneR Vegetation

Since I was new to this product, I had a bit of a steep learning curve. [BioBase Product Expert] Ray Valley provided exceptional technical support in helping resolve challenges we faced during the initial setup and navigating the BioBase output. The outputs that we obtained from BioBase using the data (tracks) we recorded included bathymetry and aquatic distribution heat maps that provided a baseline for future invasive plant monitoring in this reservoir. Since we recorded several tracks, Biobase processed them individually which provides the user with the ability to look at smaller sections or to combine areas into a larger picture. The user should check the outputs to confirm the information provided in the outputs matches known site conditions. This information will be used to guide fish surveys and inform invasive species management in the reservoir. This product performed as promised by BioBase and met our expectations. We found this to be a valuable tool that we will continue to use for additional vegetative mapping and delineation to inform management of invasive species.