Survey report for FRV "Solea" SB768: German Acoustic Autumn Survey (GERAS) 01 October - 21 October 2019
The objectives of the survey were carried out successfully and largely as planned in all of the covered ICES Subdivisions. Only in SD 21 (Kattegat), the two northernmost statistical rectangles had to be omitted due to a loss of survey time from adverse weather conditions requiring a temporal interruption of survey operations earlier. Neither the interruption nor the reduction of the surveyed area are considered to affect quality or quantity of acoustic estimates. Altogether, 1124 nautical miles of hydroacoustic transects (plus 103 nmi night and 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 45 fishery hauls were conducted. Vertical hydrography profiles were measured on 76 stations. In roughly half of all sampled rectangles, mean NASC values per nautical mile were either comparable with or higher than the values measured in 2018, and lower in the remaining rectangles. Compared to the long-time survey mean however, mean NASC values in the large majority of rectangles covered were distinctly lower. On ICES subdivision scale, mean NASC values were overall lower than in the previous year in subdivision 21, slightly higher in SD 22, distinctly lower in SD 23 and almost identical to 2018 in SD 24.