CE0701 Northwest Herring Acoustic Survey

This survey was conducted by the Marine Institute in winter 2007 as part of the North West Herring Acoustic Survey. The aim of an acoustic survey is to determine the relative abundance of the target species. This information is then used to determine catch rates and management advice for the following year. The northwest and west coast (ICES Divisions VIaS and VIIb) herring acoustic survey programme was first established in 1994. The stock in this area is composed of 2 of spawning components (autumn and winter), covering a large geographical area. Spawning occurs over a protracted period of over 4-months from late September through to late March. Since 2004 the acoustic survey has been carried out on-board the RV Celtic Explorer. The 2007 survey took place off the North West coast of Ireland, covering the area to the east of Malin Head in Co.Donegal (ICES Division VIaS) and extended west and south along the north western seaboard covering the main bays and inlets into VIIb. The survey started in the south and worked in a northerly direction to facilitate the timing of spawning within stock components. A parallel transect design was adopted with transects running perpendicular to the coastline and lines of bathymetry, where possible. Offshore extension reached up to 33 nmi (nautical miles). The acoustic data were collected using the Simrad ER60 scientific echosounder. For biological sampling, a single pelagic midwater trawl was used. 19 trawls were carried out. All components of the catch from the trawl hauls were sorted and weighed; fish and other taxa were identified to species level. Length measurements of herring, sprat and pilchard were taken. Oceanographic stations were carried out during the survey at 20 predetermined locations along the track. Not all stations were sampled due to weather conditions. Data on temperature, depth and salinity (CTD) were collected. Visual marine mammal and seabird surveys were also conducted during daylight hours. The aim of the acoustic survey is to determine the relative abundance of the target species, herring. This information is then used to determine catch rates and management advice for the following year. Other objectives include collecting physical oceanography (CTD) data and visual surveys for marine mammals and seabirds.