Research Document - 2008/062

Summary of the 2007 Herring Acoustic Surveys in NAFO Divisions 4VWX

By M.J. Power and G.D. Melvin

Abstract

Automated acoustic recording systems deployed on commercial fishing vessels have been used since 1997 to document the distribution and relative abundance of Atlantic herring in Northwest Atlantic Fisheries Organization (NAFO) divisions 4VWX from industry vessel surveys and fishing excursions. In 2007, regularly scheduled surveys at approximately 2-week intervals were again conducted on the main spawning components, and the spawning stock biomass for each component was estimated by summing these results. Four structured surveys were conducted in Scots Bay, 4 on Trinity Ledge, 3 in the Spectacle Buoy area and 5 on German Bank, with most following the established protocol. These surveys provided good coverage of the spawning areas consistent with established protocols in most cases. Additional data from fishing nights on German Bank were also examined but were not applied to the overall spawning stock biomass (SSB). Biomass estimates in the traditional survey areas for Scots Bay, Trinity Ledge and German Bank were 384,400t, which is an increase of approximately 100,000t from 2006. The 2007 SSB estimate remains below the long term average.

Biomass estimates from surveys of the coastal Nova Scotia spawning components for the Little Hope/Port Mouton, Eastern Shore and Glace Bay areas were also examined and showed declines in all areas. No acoustic surveys were conducted in the Bras d’Or Lakes in 2007. There were some large aggregations of herring observed and reported for the offshore Scotian Shelf, but no acoustic surveys were completed.

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