Browsing by Author "Helfrich, Andrew"

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    Use Of Multi-Gear Sampling To Improve Abundance Estimates Of Demersal Coregonids In The Laurentian Great Lakes
    (2023) Helfrich, Andrew
    Demersal species such as Bloater (Coregonus hoyi), Shortjaw Cisco (Coregonus zenithicus), Lake Whitefish (Coregonus clupeaformis) and Round Whitefish (Prosopium cylindraceum) play a vital role in both the Laurentian Great Lakes food webs and the commercial fishing industry. Hydroacoustic sampling has proven useful when performing stock assessments because hydroacoustics provide rapid spatial coverage as well as lower size and species selectivity compared to other assessment methods. The objective of this study is to develop an accurate hydroacoustic sampling method for measuring the abundance and distribution of Lake Whitefish and other demersal species in the nearshore habitat of the Wisconsin management unit 2 where there is an active Lake Whitefish commercial fishery. A combination of trawl and hydroacoustic data were used to develop a Classification and Regression Tree (CART) model to assign hydroacoustic targets (echoes) to species. The method was used to estimate density and biomass of Lake Whitefish of which there was an estimated 4.1 million kilograms (4,100 metric tons) (17.4 kg/ha) (95% CI: ± 22.6) in the Wisconsin management unit 2 of Lake Superior. My approach provides critical fishery independent estimates of commercially and ecologically important species in Lake Superior and should act as a baseline for further assessment of the demersal species in Lake Superior.