Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8434
Title: Acoustic classification of coexisting taxa in a coastal ecosystem
Author: Mei Sato, John K. Horne, Sandra L. Parker-Stetter, J. E. Keister
Publication Year: 2015
Journal: Fisheries Research
Volume: 172
Pages: 130-136
Keywords: acoustics,Pacific hake,Pacific herring,trawling,zooplankton
Abstract:

Classifying coexisting taxa in a coastal ecosystem remains an analytic challenge due to the difficulty in verifying species compositions within backscatter data.  Multifrequency measurements (38, 70, 120, 200 kHz) were combined with midwater trawls and zooplankton MultiNet tows in Hood Canal, WA, to classify backscatter dominated by single fish species (Pacific Herring, Pacific Hake) or major zooplankton taxa (euphausiids, copepods).  Backscatter was categorized into aggregations, single targets, and layers based on morphology.  Aggregations and single targets were identified in raw volume backscattering strength (Sv), while layers were classified using differences in mean volume backscattering strength (DMVBSi-j = MVBSi – MVBSj, where i and j denote frequency in kHz).  Based on a subset of trawl-validated in situ acoustic measurements, backscatter with -16 dB < DMVBS200-38 ≤ 2 dB were classified as fish, and 2 dB < DMVBS200-38 < 30 dB as zooplankton.  Backscatter identified as fish were further classified to hake when DMVBS120-38 < -4.8 dB, and herring when DMVBS120-38 ≥ -4.8 dB.  The classification method was evaluated using a second set of trawl-validated acoustic data, resulting in classification accuracy of fish or zooplankton ranging from 95% to 100%.  At the species level, misclassifications of herring and hake were both ~ 13%.  Removal of aggregations and single targets before calculating DMVBS values minimized the possibility of mixed species backscatter within layers.  This classification technique provides an approach to separate coexisting aggregations of dominant taxa which are common in mid- and low-latitude coastal ecosystems.

Description:

Methods paper that uses multifrequency acoustic approaches and net (trawl and zoopalntkon) to classify  coexisting species.

Theme: Ecosystem approach to improve management of marine resources
Foci: Characterize ecological interactions (e.g. predation, competition, parasitism, disease, etc.) within and among species.
Official Citation:

Sato, M., J.K. Horne, S.L. Parker-Stetter and J.E. Keister. Acoustic classification of coexisting taxa in a coastal ecosystem. Fisheries Research.