Survey Report FRV Solea / German Acoustic Autumn Survey (GERAS): 01 - 19 October 2018
In the majority of sampled rectangles, mean NASC values per nautical mile were distinctly higher than the values measured in 2017 and in SD 22 and SD 21 (in 2 and 3 cases, respectively) higher than the long-time mean values. Despite this increase from 2017, the majority of rectangles sampled in 2018 still showed mean NASC values below the long time mean. While NASC values measured were higher in ICES Subdivisions 21, 22 and 23 (in comparison with 2017), levels in SD 24 were in all but two rectangles distinctly lower than the already low NASC values measured in the previous year. While in SD 23, as in 2017, unusually low NASC values (albeit higher than in the previous year) were measured, indicating absence of the dense aggregations of herring usually observed in that area at this time of the year. On a repetition of the transect in SD 23 during daytime for comparison, NASC values measured were distinctly higher than those recorded during nighttime, indicating higher presence of clupeids in the area. For species allocation and identification, altogether 62 fishery hauls were conducted (including 58 valid hauls during the survey and 3 valid hauls on comparison transects). Vertical hydrography profiles were measured on 106 stations.