Evaluating catchability in a large-scale gillnet survey using hydroacoustics: Making the case for coupled surveys

Fisheries Research
By: , and 

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Abstract

Abundance estimates facilitate successful fisheries management. Fisheries agencies often monitor abundance through fishery independent standardized protocols generating relative measures such as catch-per-unit-effort (CPUE), where CPUE is assumed proportional to true abundance. Unfortunately, this assumption is rarely met as fish behavior and environmental conditions influence catchability and sample gear efficiency. We used paired gillnet and hydroacoustic samples and a catchability equation (Ui=qNiβ) to assess the correspondence between gillnet CPUE (Ui) and hydroacoustic abundance estimates (Ni). We found that gill nets were hyperstable (i.e., β < 1) and efficiency declined along environmental gradients. These gradients, such as increased depths, and decreased turbidity and water temperatures, likely influenced fish behavior, and encounter and gear saturation rates. As a result, catchability declined with increasing abundance qacross survey regions. Finally, simulations showed that catchability gradients and variable migratory patterns can contribute to annual variation in CPUE indices regardless of changes in abundance. Surveys plagued by varying catchability could benefit from coupling with hydroacoustics, a sample gear less subject to gear efficiency and catchability issues.

    Study Area

    Publication type Article
    Publication Subtype Journal Article
    Title Evaluating catchability in a large-scale gillnet survey using hydroacoustics: Making the case for coupled surveys
    Series title Fisheries Research
    DOI 10.1016/j.fishres.2018.11.009
    Volume 211
    Year Published 2020
    Language English
    Publisher Elsevier
    Contributing office(s) Great Lakes Science Center
    Description 10 p.
    First page 309
    Last page 318
    Other Geospatial Lake Erie
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