GNSGerBT3 | Greater North Sea German Beam Trawl Quarter 3 Groundfish Survey Monitoring and Assessment Data Products

The Greater North Sea German Quarter 3 Beam Trawl Groundfish Survey Monitoring and Assessment Data resource contains both biological and sampling information. There are two sampling areas a “Full” data set, this includes rectangles that have a poor temporal sampling record. The “SSA” or “Standard Survey Area” sampling area only contains rectangles that have consistent temporal sampling and meet the criteria set out in Moriarty et al, (2017).The “sampling information” contains all the technical information required to describe each individual haul. The “biological information” contains all of the biological information required to describe the species length and weight distributions in each haul. Biological information is further classified by “baseline” data. This data contains a mix of species, genus, and family classifications, with a tag to say if it required further assessment and “null” length values, with a tag to say a length frequency distribution needs to be assigned. The “k-NN” or “k” number of nearest neighbours data has reconciled all of the taxonomic data to the highest resolution possible, and assigned an appropriate length distribution to the sample in question.Product type:•This product is the Full Standard Monitoring Programme it is recommended that you use the Standard Survey Area - Standard Monitoring Programme for any OSPAR related analyses. •This product is the Standard Survey Area - Standard Monitoring Programme this is the recommended product for all analyses. •This product is the baseline/non-resolved biological information, this contains species and length classes that have not been resolved. We recommended use of the knn/resolved product for all analyses. •This product is the knn/resolved product which is recommended for all analyses. Additional information:This data can be freely downloaded according to the Scottish Government data policy.

Data quality statement:This data product has undergone rigorous quality checking, as outlined in the supporting documentation (Moriarty et al, 2017; Greenstreet et al 2017). It is suitable for supporting OSPAR fish community assessments and additional indicator research and development. Data source:Data was sourced on the Database of Trawl Surveys (DATRAS) housed by ICES, this data is traditionally used for stock assessments and fish community studies by the ICES community and public users. The ICES data have to pass an extensive quality check. Collection methods:The data was collected by the Thünen Institute of Sea Fisheries during their Beam Trawl Survey (BTS) coordinated by the Beam Trawl Survey Working Group. Data processing methods:While DATRAS has an integrated quality check, it was necessary to do a more extensive quality check and estimate certain values when data was not originally collected. The processing methods are fully outlined in Moriarty et al (2017). Data Interoperability:Sampling InformationField-Unit-DescriptionHaulID- -Unique haul identifier (SurveyAcronym/Ship/Year/HaulNo) (H)Survey-Acronym- -Unique survey identifier (SubregionCountryGearTypeQuarter: e.g. GNSNedBT3)Ship- -Unique vessel identifier (e.g. SCO3: Scotia III)GearType- -Unique gear type code (BT = Beam Trawl, OT = Otter Trawl)Gear- -Unique gear code (e.g. GOV = Grande Oerverture Verticale)YearShot- -Year that gear was shotMonthShot- -Month that gear was shotDayShot- -Day that gear was shotTimeShot-GMT-Time that gear was shot (in format HHMM)HaulDur(min)-Min-Duration of fishing operationShootLat(decdeg)-Deg.-Latitude in decimal degrees of the haul shoot positionShootLong(decdeg)-Deg.-Longitude in decimal degrees of the haul shoot positionICESStSq- -ICES statistical rectangle where gear was shotSurvStratum- -Stratum tag for stratified surveysDepth(m)-m-Depth tag assigned to the haulDistance(km)-km-Tow distance (dH,TOW)WingSpread(m)-m-Mean distance between the wings during fishing operation(dH,WING)DoorSpread(m)-m-Mean distance between the doors during fishing operation (dH,DOOR)NetOpen(m)-m-Mean head-line height above seabed during fishing operation (dH,HEIGHT)WingSwptArea(sqkm)-km2 -Area of seabed swept by the net (AH,WING = dH,TOW x dH,WING)WingSwptVol_CorF- -Multiplier (1 / dH,HEIGHT): converts to ‘density by wing-swept volumeDoorSwptArea_CorF- -Multiplier (dH,WING / dH,DOOR): converts to ‘density by door-swept areaDoorSwptVol_CorF- -Multiplier (dH,WING / (dH,DOOR x dH,HEIGHT)): converts to ‘density by door-swept volumeBiological InformationThere are two Biological Information data products, ‘BaseLine’ and ‘KNN’. In ‘Baseline’ the k-NN procedure has not been applied, so densities-at-length of species complexes (e.g. genus, family or order taxonomic resolution level identifications codes) have not been resolved to the complexes constituent species, densities of a species where length data are not provided have not been resolved to their constituent length categories, and destinies of species complexes have not been resolved to their constituent species and length categories. In ‘KNN’ the k-NN procedure has been applied to address these three type of problem. Consequently the ‘KNN’ data product will have more records that the ‘Baseline’ data product and some fields are not relevant to the ‘Baseline’ data product. The ‘KNN’ data product will have the following structure.Field-Unit-DescriptionHaulID- -Unique haul identifier (SurveyAcronym/Ship/Year/HaulNo) (H)SpeciesSciName- -Unique species name for each species sampled across the NE Atlantic (S)FishLength(cm)-cm-Integer numbers indicating fish length to the ‘cm below’ (L)IndivFishWght(g)-g-Estimated weight of individual fish of specified species and length (WS,L)Number- -Total number of fish of specified species and length in the catch (NS,L,H)DensAbund(N_sqkm)-km-2-Abundance density estimate (Dnos,S,L,H = NS,L,H / AH,WING)DensBiom(kg_Sqkm)-kg km-2-Biomass density estimate (Dbiom,S,L,H = (NS,L,H x WS,L)/ AH,WING) The ‘BaseLine’ product will not include the fields IndivFishWght(g) and DensBiom(kg_Sqkm), and the field SpeciesSciName will simply be called SciName. The two fields are excluded because with uncertain species identities it would not be possible to consistently include data for the field IndivFishWght(g), and in addition with uncertainty regarding length category, estimation of appropriate reliable values for the field DensBiom(kg_Sqkm) would also not always be possible. The ‘BaseLine’ data product was included because of feedback from data providers and potential data users, who stated that they would prefer having access the “real” data, rather than rely on estimated values to fill in where information was missing.