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Single-Beam Echosounder

Eastern Bering Sea Hydroacoustic Survey

This pilot study investigates use of a Simrad EK-500 single beam echosounder for characterization and mapping of EBS groundfish habitats. Approximately 6 million echoreturns from the seafloor were simultaneously collected at two frequencies (38 and 120 kHz) during a 1999 hydroacoustic fishery survey by the NOAA ship MILLER FREEMAN. A total of 9,000 miles of EBS seabed was sampled.

Seabed classess along survey trackline. Click to enlarge image in a new window.Click to enlarge image in a new window.

Distribution of Q1 values (the first principal component) derived
from single-beam echosounder parameters along survey trackline

Numerical parameters were extracted from the digitized echoreturns using QTC VIEW software and then reduced to principal components (Q-values). The three most important principal components (Q1, Q2, Q3) were used in GAM statistical models to evaluate the degree to which these continuous-valued acoustic data could explain the distribution and abundance of commercially important species. The best models explain 31-77% of variability in eight groundfish and two crab species, based on data from 23 years of RACE bottom trawl surveys. The acoustic data contributed 213% of these totals.

Collaborative research with the Quester Tangent Corporation has also resulted in a fully-automated objective classification process involving a new application of the Bayesian Information Criterion (BIC). The resultant optimal classification scheme has identified 14 distinct classes of bottom types for the EBS shelf based on 38 kHz data.

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