Research Document - 2007/031

Summary of the 2006 Herring Acoustic Surveys in NAFO Divisions 4VWX

By Power, M.J., G.D. Melvin and L.M. Gosse

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 NAFO Division 4VWX from industry vessel surveys and fishing excursions. In 2006 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. Three structured surveys were conducted in Scots Bay, five on Trinity Ledge and four on German Bank with most following the established protocol. Except for the Trinity Ledge area these surveys provided good coverage of the spawning areas consistent with previous years. Additional data from fishing or survey nights in Scots Bay, German Bank, Browns Bank, Seal Island and Spectacle Buoy areas were also examined. Biomass estimates for Scots Bay, Trinity Ledge and German Bank were approximately 28,600t, 8,500t, and 245,500t for an estimated total SSB of 282,600t in the traditional survey areas, which is an increase from 2005 but still a substantial decrease from previous years. An additional 18,300t was surveyed outside of the standard survey areas.

Biomass estimates from surveys of the coastal Nova Scotia spawning components for the Little Hope/Port Mouton and Eastern Shore areas were also examined. There was a relatively large decrease in the Little Hope area while the Eastern Shore area saw a substantial increase from the previous year. A survey with an acoustic recorder had been completed in 2005 for the Glace Bay area but was not repeated in 2006. There was again no acoustic survey effort in the Bras d’Or lakes. There were some large aggregations of herring observed and reported but no acoustic surveys were completed for the offshore Scotian Shelf.

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