The cruise was part of an international hydroacoustic survey providing information on stock parameters of small pelagics in the North Sea (HERAS - North Sea, West of Scotland and Malin Shelf summer acoustic survey), coordinated by the ICES Planning Group for Herring Surveys. Denmark, the Netherlands, Norway, Scotland and Ireland also participated in the survey. In general, this survey provides the most important fisheries independent contribution to the assessment of herring stocks in the North Sea, Western Baltic Sea, Skagerrak/Kattegat as well as areas west of Scotland and the Irish Sea. The total survey area largely covers ICES Divisions IIIa, Iva, Ivb and Via, with the area covered by FRV Solea comprising the southern North Sea from 52° to 56° N. Main focus was set on herring (Clupea harengus), whereas the evaluation of sprat (Sprattus sprattus) stocks was another objective of the survey. Due to mostly very favorable weather conditions, the whole survey area, i.e. All transects could be covered as originally planned. Altogether, 1875 nm of hydroacoustic transects were sampled. Recording of hydroacoustic data usually took place between 06:00 and 20:00 (6 am to 6 pm) with an occasional extension of the daily sampling to ca. 21:00 (9 pm) according to survey progress. To allocate biological information to echorecordings and for the collection of biological samples, altogether 35 fishery hauls were conducted. Generally, sprat showed the highest presence in fishery hauls and also contributed the bulk biomass to total catch weight, followed by herring. Altogether, the total number of fish species caught was lower than in the previous year (17 and 24 respectively). Hydrography profiles were measured with a vertically deployed CTD probe on 80 stations.
Matthias Schaber (Thünen Institute of Sea Fisheries, Hamburg)
ICES North Sea Herring Acoustic Survey
International Council for the Exploration of the Sea (ICES)