Plattform Platform	Reise-Nr. Cruise-No.	Zeitraum Period	Projekt Project	Arbeitsgebiet Working area
Solea	710	01.10.2015 - 19.10.2015	BIAS	Baltic Sea

Fahrtleiter Chief Scientist	Institut Institute	Auslaufhafen Port of departure	Einlaufhafen Port of return	Stationskarte Station map	Schiffsroute Trackchart
Grohsler Tomas	Thunen-Institut fur Ostseefischerei	Rostock	Rostock	Karte Map

Ziel der Reise / Objectives of Cruise:

Objectives: International autumn acoustic survey for pelagic stocks in the Baltic Sea (BIAS) Narrative: The cruise was part of an international hydroacoustic survey providing information on stock parameters of small pelagics in the Baltic Sea, coordinated by the ICES Planning Group for Herring Surveys. FRV "Solea" participated for the 28th time. The survey area covered the western Baltic Sea including Kattegat, Belt Sea, Sound and Arkona Sea (ICES Subdivisions 21, 22, 23 and 24). Overall regular cruise track length was 1 230 nm. In almost all rectangles surveyed, mean NASC values per nautical mile were distinctly below the observations recorded in 2014 and also below the long-time survey average. On ICES subdivision scale, mean NASC values were lower than in the previous year in SD 21, 22 and 24 while in SD 23 mean NASC values were higher than in 2014. In SD 21, mean NASC per 1 nm EDSU was lower in than both the previous year and the long-time survey average in all rectangles surveyed. As in the previous year, increased aggregations of clupeids were measured in the northern part of the Kattegat (rectangle 43G1), but mean and overall NASC values also in this area were significantly lower than in 2014. Also in SD 22, mean NASC values recorded were lower than the previous year and the survey average in all rectangle surveyed. Notable but small aggregations of clupeids were only recorded in the western part of Kiel Bight (38G0) and north/east of Fehmarn Island (38G1, 37G1) while the distribution was irregular along the rest of the survey transect in the remaining parts of the subdivision. The large aggregations of big herring that can be observed annually in SD 23 in the Ore Sound were again present in autumn 2015. NASC values in rectangle 40G2 covering the aggregation hotspot in this area were slightly lower than the high levels measured in 2014 but still significantly higher than the long-time survey average. Like in 2014 the herring aggregations expanded north towards the narrow Helsingor/Helsingborg strait into rectangle 41G2 with corresponding NASC values similar to the previous year. As in 2014, highest fish densities in SD 24 were recorded north and east of Rugen Island and also in the central parts of the Arkona Sea (37G3, 38G3 and southern 39G3). In most of the rectangles surveyed however, mean NASC values were lower than in the previous year. In rectangles 38G4 (southeastern Arkona Sea) and 39G2 (northwestern Arkona Sea, near Ore Sound mouth), NASC values were above the 2014 results (but below average). For species allocation and identification, altogether 59 fishery hauls were conducted.

Messungen / Measurements