Northwest Herring Acoustic Survey Report 2006

Abstract

The northwest and west coast herring acoustic survey programme was first implemented in 1994. Prior to this a larval survey programme was carried out between 1981 and 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). The stock in this area is composed of 2 spawning components (autumn and winter), covering a large geographical area. Spawning may extend over a 4 month period from late September through to late March (Molloy et al, 2000). Traditionally fishing activity has targeted spawning and pre-spawning aggregations, no summer matje fishery exists in this area, as is the case in the Celtic Sea. In VIaS, fishing has traditionally taken place in late October and continues until late February (winter spawners). Traditionally in VIIb, fishing is mainly concentrated on the later months of the year and would be concluded by the early part of the new year (Autumn spawners). The protracted spawning period of herring and the overlap between the two spawning stocks in this area (October to February) is highly dynamic with variations between annual spawning events of up to 3 weeks. Accurate survey timing is a key component of the design to cover the overlap of peak spawning events. A project is currently underway to describe stock structure and discrimination of herring around Ireland. The results of this project may have implications for the design of this survey and for the stock assessment. However, since 1994, acoustic surveys have been carried out, and currently are the only tuning indices available. The current survey makes up the 13th in the time series. The design and execution of this survey has evolved from summer feeding phase surveys, in the mid 1990s until its present winter spawning state. This is the third survey of this stock carried out by the Celtic Explorer.