Research Document - 2004/31

Summary of the 2003 Herring acoustic surveys in NAFO Divisions 4VWX

By Melvin, G.D., Power, M.J., Annis, L,M., Clark, K.J., Fife, F.J., Stephenson, R.L.

Abstract

Automated acoustic recording systems deployed on commercial fishing vessels were used to document the distribution and abundance of Atlantic herring in NAFO Division 4VWX from industry vessel surveys and fishing excursions. Regularly scheduled surveys, at approximately 2-week intervals, were conducted on the main spawning components and the spawning stock biomass (SSB) for each component was estimated by summing these results.

In 2003, three surveys were conducted in Scots Bay, three on Trinity Ledge and five on German Bank following established protocol, and provided good coverage of these spawning areas consistent with previous years. Additional data from fishing nights in Scots Bay and German Bank were examined. On German Bank, a 22 day gap between surveys, as well as equipment failure during the documentation of a large spawning aggregation, may have led to an underestimate of total SSB. There were also equipment problems during the first Scots Bay survey which resulted in the loss of data from transects containing dense areas of fish. Biomass estimates for Scots Bay, Trinity Ledge and German Bank were approximately 133,900t, 14,500t, and 343,500t for a total SSB of 493,300t in the traditional survey areas. A single fishing night recording near Seal Island observed 12,200t and 1,400t of spawning fish were documented in the spring near Spectacle Buoy. The total estimated SSB for the Bay of Fundy/SW Nova Scotia component of the 4WX herring complex in 2003 spawning season was 505,500t. While this represents a slight decrease, it is not considered significantly different from 2002.

Biomass estimates from surveys of the coastal Nova Scotia spawning components were higher in 2003 with large increases in estimated spawning biomass for the Little Hope/Port Mouton, Eastern Shore and Glace Bay areas. For the offshore Scotian Shelf there were no large aggregations of herring observed and no acoustic surveys were conducted. There was no acoustic survey effort in the Bras d'Or lakes.

Complete document (PDF, 1063 KB)

Accessibility Notice

This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.