A multifrequency method to classify and evaluate fisheries acoustics data

Abstract

Acoustic surveys have been conducted on Georges Bank from 1998 to present to estimate Atlantic herring (Clupea harengus) population abundance. Acoustic data were collected with a 12 or 18, 38, and 120 kHz Simrad EK500 scientific echo sounder. A pelagic trawl and underwater video images were used to collect biological information and to verify the species composition of acoustic backscatter. A multifrequency classification method was developed to improve the efficiency and accuracy of classifying species from acoustic echograms. In this method, a volume backscatter (Sv) threshold was applied equivalently to all echograms, and then a composite echogram was created based on which frequencies had Sv greater than or less than the Sv threshold. The results of this method were compared with the standard method of visually scrutinizing regions, and metrics were developed to evaluate the accuracy of classification algorithms relative to current methods, as well as to assess the effects of classification methods on population abundance estimates. In general, this method matched visually scrutinized Atlantic herring regions, but with consistent biases in classifying 38 kHz backscatter. The metrics highlighted spatial and temporal changes in the acoustic landscape, which may be indicative of intra- and inter-annual biological changes.

Aggregative patterns of pre-spawning Atlantic herring on Georges Bank from 1999-2010

“…Data collected during 1999-2004 are detailed in Jech and Michaels (2006). Data collected during [2005][2006][2007][2008] with the EK500 are identical to Jech and Michaels (2006).…”

“…In this study, classification is not the goal, as the aggregations are known to be herring (e.g., Jech and Michaels 2006), but a spatial and temporal examination of morphological, positional, and energetic metrics (Reid 2000) was conducted to elucidate how stable herring pre-spawning behavior was in relation to the survey timing and spatial extent.…”

Winter distribution and size structure of Antarctic krill Euphausia superba populations in-shore along the West Antarctic Peninsula

“…High concentrations of euphausiids have been observed in canyons and shelf break regions globally (e.g. Gulf of St. Lawrence: Simmard et al 1986, Sourisseau et al 2006, 2008Georges Bank: Greene et al 1988, Jech & Michaels 2006Bering Sea: Coyle & Cooney 1993;WAP: Lawson et al 2004). Along the WAP, concentrations of krill in canyons have been particularly noted at the head of Palmer Deep Canyon (Bernard & Steinberg 2013), and at the head of the canyon north of Livingstone Island (Warren et al 2009).…”

Broadband classification and statistics of echoes from aggregations of fish measured by long-range, mid-frequency sonar

“…These echosounder data were processed by the NEFSC team using a combination of manual analysis and automated classification and detection algorithms to identify schools of fish with gas-filled swimbladders, classify these aggregations into Atlantic herring (Clupea harengus) and non-herring schools, and extract parameters for each school (e.g., school depth, school length, school thickness, and volume backscattering strength). 25,26 C. Biological sampling (NOAA-NEFFC)…”