Herring larvae surveys in the North Sea and adjacent waters in 1975/76 and 1976/77

Because of a systematic error in calculating the numbers of herring larvae per square metre surface, caught by one country, the results of the North Sea herring larval surveys in 1975/76 have had to be reappraised. These data, and those collected in 1976/77 are presented in this paper. They suggest that larval production in 1975, in all areas except Buchan, was considerably less than in preceding years. In 1976 larval production remained at a generally low level, although there was some increase in estimated abundance in the Shetland/Orkney area. Spawning stock sizes in the northwestern North Sea and in the Whitby/Dogger area, as estimated from a regression of larval abundance on spawning stock size, are 79 000 tons in 1975 and 87 000 tons in 1976 for these areas combined. These estimates are rather lower than those produced by the Herring Assessment Working Group for the Area South of 62°N from fisheries data. Some factors which have a bearing on the planning of future surveys and on the utilisation of these data for the estimation of stock size are discussed.