Research Document - 2011/093

Distribution and intensity of acoustic backscatter of key species identified in the 2008 fall bottom trawl survey in NAFO Divisions 2J3KLNO

By L.G.S. Mello, G.A. Rose, F.K. Mowbray, and M. Koen-Alonso

Abstract

This study investigated the suitability of using the acoustic and catch data gathered during bottom trawl surveys conducted in Newfoundland and Labrador waters (NAFO Div. 2J3KLNO). The main goal is to improve abundance and distribution estimates of key fish species of the shelf ecosystem, in particular for small pelagic forage fish species. First, we describe the methodology used for acoustic data collection and editing, fish species identification and problems encountered. Next, we compare the acoustic estimates (backscattering coefficient, sa) for different fish species with the catch data from the 2008 fall bottom trawl tows. We also present acoustic estimation along the survey tracks. The integrated analysis of acoustic and catch data was successful in (i) detecting and differentiating among several groups of organisms across the continental shelves of Newfoundland and Labrador, including zooplankton, pelagic (capelin and sandlance) and demersal fish (cod, redfish, myctophids), (ii) providing proxy estimates of density and distribution for different groups of fish, (iii) identifying the role of factors such as geographic location and bathymetry, which seem to affect the distribution pattern of the various fish groups.