Survey report for FRV SOLEA / German Acoustic Autumn Survey (GERAS): 01 - 19 October 2018
The objectives of the survey were carried out successfully and as planned in all of the covered ICES Subdivisions. Adverse weather conditions occurred during the first night of the survey in the southwestern part of SD 22 (Kiel Bight) but did not require interruption of survey operations and are not considered to affect acoustic estimates (see below). Altogether, 62 trawl hauls were carried out during the survey providing biological data for age stratified abundance estimation of target species herring and sprat (58 valid hauls utilized for estimates). Measured NASC values per 1 nmi EDSU allocated to clupeids were higher in most parts of the survey area compared with the previous year (exception SD 24), but below the long-term survey mean. A further decrease in abundance of Western Spring Spawning Herring (-22% and -49% in SD 21-24 and 22-24 respectively) was recorded to the second lowest levels of the time-series since 1993. Abundance increased (+56% and +19% respectively) due to a high contribution of 0-group herring. In sprat, abundance and biomass in the survey area declined by 37 % and 43% respectively. As in the previous years, dense aggregations of large, mature herring seemed to be absent from their overwintering area in SD23.