1993 ICES coordinated acoustic survey of ICES Division IVa, IVb and VIa

Summary: This paper provides a report on the combined acoustic survey of herring stocks in the North Sea and ICES division IVaN in June-July 1993. The surveys were carried out by Norway, Scotland, Denmark and Netherlands and covered the period 29 June to 30 July. The results and distributions of herring by age are given for area by 30 Nmile statistical rectangles. The results are expressed in biomass and numbers of fish. In addition data on ichthyophonus infection rates determined from trawl samples obtained on the survey are reported and the infected numbers and proportions of the population are estimated. A discussion of errors in the estimation of abundance is included in the report