In the southwest of Ireland and the Celtic Sea (ICES Divisions VIIaS, g & j),herring acoustic surveys have been carried out since 1989. In the Celtic Sea and VIIj, herring
acoustic surveys have been carried out since 1989, and this survey is the 21st in the
overall acoustic series or the tenth in the modified time series conducted exclusively in
October.
The geographical confines of the annual 21 day survey have been modified in recent
years to include areas to the south of the main winter spawning grounds in an effort to
identify the whereabouts of winter spawning fish before the annual inshore spawning
migration. Spatial resolution of acoustic transects has been increased over the entire
south coast survey area. The acoustic component of the survey has been further complemented since 2004 by detailed hydrographic, marine mammal and seabird surveys
