Northwest Herring Acoustic Survey Report 18 June – 07 July, 2011

Abstract

The northwest and west coast (ICES Divisions VIaS & VIIb, c) herring acoustic survey programme was first established in 1994. Prior to acoustic estimation, a larval survey programme was conducted from 1981-1986. In the early 1990s, the ICES herring working group (HAWG) identified the need for a dedicated herring acoustic survey in this area (Anon, 1994). From 1994 to 1996 surveys were carried out on this stock during the summer feeding phase. In 1997 a two-survey spawning survey was established covering both autumn and winter components. In 2004, this was modified into single spawning stock survey was carried out early in quarter 1 which continued until 2007. In 2008, it was decided that this survey should be incorporated into the larger coordinated Malin shelf survey on recommendation from SGHERWAY and WGHAWG. The summer 2011 survey represents the forth in the new time series (est. in 2008). The Irish component was carried out to cover, 1) the regions around western Ireland 2) the regions west of Scotland that are usually covered Marine Scotland and 3) northern sector of the Irish Sea survey (AFBI). The survey was coordinated through the ICES Working Group of International Pelagic Surveys (WGIPS). Combined survey data on herring distribution, abundance and age are used to provide a measure of the relative abundance of herring within the Malin shelf stock complex. Survey data on stock numbers at age are submitted to the ICES Herring Assessment Working Group (HAWG) and used in the annual stock assessment process. The northwest and west coast (ICES Divisions VIaS & VIIb) herring stock is composed of 2 of spawning components, autumn and winter spawners. Spawning covers a large geographical area and extends over a 4-month period from late September through to late March (Molloy et al, 2000). Traditionally fishing effort has been concentrated on spawning and pre-spawning aggregations. The autumn spawning component, which mostly occurs within VIIb and VIaS, feeds along the shelf break area to the west of the spawning grounds. The winter spawning component is found further north in VIaS. In VIaS, summer distribution extends from close inshore to the shelf break. Components of the winter spawning fish are known to undertake northward feeding migration into VIaN before returning in the winter to spawn along the Irish coast.