Hydroacoustics
Dr. Jacobson conducted his master's and Ph.D. research using hydroacoustic methods. His hydroacoustic project experience includes studies of fish size, abundance, distribution, and behavior. He has designed hydroacoustic surveys, collected acoustic data in freshwater (both lotic and lentic systems), estuarine, and marine environments, and analyzed acoustic data using a variety of analytical tools. He has also developed a sonar and signal processor simulator to support direct, quantitative comparisons of hydroacoustic data with three-dimensional, individual-based simulations of fish behavior.
Evaluation of Single-beam Methods for Assessing Fish Size and Abundance
The accuracy of size estimates and the precision of abundance estimates derived from single-beam sonar data were evaluated in a 800 hectare, northern Wisconsin lake. The acoustic methods were found to provide accurate size estimates for fish vulnerable to experimental gill nets. The acoustic methods also detected fish in a size range invulnerable to the gill nets. Analysis of repeated transects demonstrated that the acoustic methods have a high degree of precision; however, variability among and within transects was very high, indicating that large-scale distribution of fish in a water body is an important consideration for reliable estimation of abundance. The results of this study were used to substantially modify hydroacoustic sampling protocols that had been in use for several years by the NSF-sponsored North Temperate Lakes Long Term Ecological Research program. This work was supported by a contract between the University of Wisconsin-Madison Center for Limnology and the Office of Naval Research.
This project is also described under the following project category:
Monitoring and Long-term Research
Acoustic Estimation of Fish Abundance for a Whole-Lake Biomanipulation Study
Hydroacoustic surveys were designed, implemented and analyzed to provide absolute estimates of planktivore abundance for an experimental biomanipulation study in Lake Mendota, Wisconsin. The study examined the ability of lake managers to reduce algal biomass through top-down manipulation of the food web (i.e. stocking of piscivores). Repeated acoustic surveys, conducted to track changes in the abundance of pelagic planktivores, documented a 95% decline in planktivore abundance. This work was funded by a grant from the Wisconsin Department of Natural Resources to the University of Wisconsin-Madison Center for Limnology.
This project is also described under the following project categories:
Monitoring and Long-term Research
Lake, Stream, and Watershed Management and Restoration
Hydroacoustic Investigation of Temporal-Spatial Patterns in the Distribution of a Pelagic Fish
Acoustic surveys conducted to assess the abundance of cisco (Coregonus artedi) in Trout Lake, Wisconsin, revealed that this pelagic planktivore exhibited large-scale, dynamic, recurring patterns of distribution within the lake. Further acoustic investigation revealed that small cisco were vertically segregated from large cisco and exhibited a different temporal-spatial pattern of dispersion. Small fish, which were relatively high in the water column (10-20m depth), aggregated into dense schools after sunrise, and remained aggregated throughout the day where their depth distribution intersected the bottom. At dusk they dispersed horizontally, and remained dispersed all night. Large cisco tended to be relatively deep in the lake (>20m), and were dispersed throughout the diel period. Day-to-day variability in the horizontal distribution of cisco occurred at a large scale during both day and night. A spatially-explicit, individual-based model of schooling behavior and an animal movement simulator to execute the model were developed to examine the transient process of school development. The model produced realistic schooling behavior. A sonar and signal processor simulator was developed to sample the three-dimensional model volume and produce data directly comparable to hydroacoustic data collected in the lake. Correspondence between the simulations and hydroacoustic data from Trout Lake supported the behavioral hypotheses comprised by the model.
This project is also described under the following project category:
Fish Behavior
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