Plattform Platform	Reise-Nr. Cruise-No.	Zeitraum Period	Projekt Project	Arbeitsgebiet Working area
Solea	798	08.10.2021 - 28.10.2021	BIAS	Kattegat ICES-Subarea 22 (also ICES-subarea IIIc) Arkona Basin Baltic Sea ICES-Subarea 21 ICES-Subarea 24 (part of ICES-subarea IIId) ICES-Subarea 23 (also ICES-subarea IIIb)

Fahrtleiter Chief Scientist	Institut Institute	Auslaufhafen Port of departure	Einlaufhafen Port of return	Stationskarte Station map	Schiffsroute Trackchart
Schaber Matthias	Thunen-Institut fur Ostseefischerei	Rostock	Rostock

Ziel der Reise / Objectives of Cruise:

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 Working Group of International Pelagic Surveys (WGIPS) and the ICES Baltic International Fish Survey Working Group (WGBIFS). Further WGBIFS contributors to the Baltic survey are national fisheries research institutes of Sweden, Poland, Finland, Latvia, Estonia and Lithuania. FRV "Solea" participated for the 34th time. The survey area covered the western Baltic Sea including Kattegat, Belt Sea, Sound and Arkona Sea (ICES Subdivisions (SD) 21, 22, 23 and 24). The survey effort was comparable to 2020, although two statistical rectangles in the northern part of SD 21 could not be covered. Altogether, 1124 nautical miles of hydroacoustic transects (plus 67 nmi daytime transects for comparison) were covered. For species allocation and identification as well as to collect biological data for an age stratified abundance estimation of the target species herring and sprat, altogether 50 fishery hauls were conducted. Vertical hydrography profiles were measured on 90 stations. In all subdivisions covered, mean NASC values per nautical mile per ICES statistical rectangle were equally either distinctly lower or distinctly higher than the values measured in 2020. However, compared to the long-time survey mean since 1991, mean NASC values were lower in all but two rectangles covered. On ICES subdivision scale, mean NASC values were overall distinctly lower than in the previous year in subdivisions 21 and 22, slightly increased in SD 24, and almost fivefold increased in SD 23 (refer to cruise report for explanation).

Messungen / Measurements