Hydroacoustics

Hydroacoustics

MaxDepth Aquatics uses the latest in BioSonics hydroacoustic equipment linked with Trimble DGPS for analysis of bathymetry, substrate classification, macrophyte delineation, and fisheries assessment. These four elements form the basic suite of data inputs for aquatic habitat characterization. Within each of these major groups there are components of the analyses that can be tailored to specific applications as described below:

Bathymetry

Knowledge of the amount of water and depths in any aquatic system is essential for management of the water quantity and water quality. The intensity of the survey effort can be adjusted to accommodate a variety of needs ranging from simple exploratory maps to high-resolution bathymetry of specific features of a system. Shown below on the left is a high resolution image of the channel excavated at the outlet of Diamond Lake, Oregon in 1954 to lower the lake stage prior to treatment with rotenone. The bathymetry map on the right is of Lava Lake, Oregon.

Substrate Classification

The echoes generated from the hydroacoustic signal provide information regarding the regularity and reflectivity of the substrate. These signals can be assessed separately or as a statistical combination to provide an indication of the nature of the substrate. Unsupervised classifications of substrate composition can be further refined by collecting sediment samples in the study domain to develop supervised classifications of the substrate such as organic detritus, sand, cobble, and vegetation.


Macrophyte Delineation

The hydroacoustic surveys are extremely valuable for locating the spatial extent, canopy height, and density of submerged macrophytes. As with the substrate classifications, the macrophyte mapping can be further enhanced through the use of a designed macrophyte sampling program to generate macrophyte maps that illustrate spatial patterns among taxa.



Fisheries Assessment

Hydroacoustics provides precise information regarding the spatial distribution of fish within lakes, reservoirs and estuaries. The hydroacoustics can be deployed in an exploratory fashion to develop an information base on fish locations in previously unsurveyed waters or can be used in a rigorous sampling design over prescribed tracks to quantify the abundance of fish and their size distribution. Repeated surveys in multiple seasons aid in better understanding the use of various habitats and fish behaviors under spawning and feeding conditions. Again, the fisheries assessment with hydroacoustics can be complemented by simultaneous use of traditional netting techniques to provide verification of the observed targets and to better sample in shallow, weedy areas of lakes.


Echograms from Odell Lake showing large aggregations of kokanee schooled up during the day and the dispersal of fish during the night.