Research Document - 2003/034

Herring acoustic surveys for 2002 in NAFO Divisions 4WX

By Melvin, G.D., Annis, L.M., Power, M.J., Clark, K.J., Fife, F.J. and 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. As in previous years the data were collected during both industry vessel surveys and fishing excursions. Regularly scheduled surveys, at approximately 2-week intervals were conducted on the main spawning components in accordance with the planned program. The spawning stock biomass for each component was estimated by summing the results of surveys undertaken over the spawning season at scheduled intervals (i.e., >10 day). In 2002, 3 surveys were conducted in Scots Bay, 2 on Trinity Ledge and 2 on German Bank following established protocol and providing good coverage of the spawning areas consistent with previous years. Additional data were from 1 fishing night in Scots Bay and 3 fishing nights on German Bank to estimate the total SSB of the individual spawning components. Survey coverage of Trinity Ledge was extremely poor and is unlikely to represent the SSB. Biomass estimates for Scots Bay, Trinity Ledge and German Bank were approximately 141,000t, 8,100t, and 393,000t for a total SSB of 542,000t in the traditional survey areas. A single survey around Seal Island documented 1,240t of spawning fish and no data were available for Browns Bank. The total SSB for the Bay of Fundy/SW Nova Scotia component of the 4WX herring complex in 2002 spawning season was estimated to be 543,000t. This represents a significant increase over the previous year and removed much of the concern over the large decline in SSB for German Bank.  Biomass estimates for surveys of the coastal Nova Scotia spawning components were significantly higher in 2002. No large aggregations of herring were observed on the offshore Scotian Shelf and acoustic surveys were conducted in the Bras d'Or lakes.

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