The survey was part of an international hydroacoustic survey providing information on stock parameters of small pelagics (Acoustic Survey in the Skagerrak and Kattegat, the North Sea, West of Scotland and the Malin Shelf area, HERAS) coordinated by the ICES Working Group of International Pelagic Surveys (WGIPS). Denmark, Ireland, the Netherlands, Norway and Scotland 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.
The survey design has been standardized across participants and the survey area is partitioned into 23 strata out of which four strata comprising the southern North Sea have been allocated to Germany and were covered during this survey. Main focus was set on herring (Clupea harengus) and sprat (Sprattus sprattus), whereas distribution patterns and abundance of anchovy (Engraulis encrasicolus) as well as sardine (Sardina pilchardus) were another objective of the survey.
Altogether, 1427 nautical miles of hydroacoustic transects were covered, which is less than planned. Adverse weather conditions at the beginning of the survey and also during the course of the survey led to the loss of several survey days which had to be compensated through an adapted survey design. Accordingly, transect spacing was increased and transects were dropped in strata 51, 71 and 131. Nevertheless, the whole survey area was covered and all strata were sampled.
Matthias Schaber (Thünen Institute of Sea Fisheries, Bremerhaven)
International Council for the Exploration of the Sea (ICES)