DOI: 10.14466/cefasdatahub.126
title: A data product derived from Northeast Atlantic groundfish data from scientific trawl surveys 1983-2020

description: This is a data product to support state indicators that are based from groundfish biological data, derived using primary data from surveys undertaken in the Northeast Atlantic between 1983 and 2020. Catch records by taxonomic group and by length category in terms of biomass and numbers of fish standardised to duration (per hour) or to the area swept by the haul. Data are available from multiple surveys using data downloaded from the ICES database of trawl surveys (DATRAS) once quality-controlled and standardised following procedures detailed in Greenstreet and Moriarty 2017. Data file names reflect the OSPAR region sampled, country conducting the sampling, fishing gear and time of years of sampling (as defined by Greenstreet and Moriarty 2017), e.g.: BBICFraBT4 refers to Bay of Biscay and Iberian Coast data from France by a Beam Trawl survey in quarter 4 of the year and GNSIntOT3 refers to Greater North Sea data from International (multiple countries) sampling by an Otter Trawl survey in quarter 3 of the year etc.
Greenstreet, S.P.R. and Moriarty, M. (2017) OSPAR Interim Assessment 2107 Fish Indicator Data Manual (Relating to Version 2 of the Groundfish Survey Monitoring and Assessment Data Product). Scottish Marine and Freshwater Science Vol 8 No 17, 83pp. DOI: 10.7489/1985-1
Scientific survey data collected by multiple countries and made available through ICES DATRAS (https://www.ices.dk/data/data-portals/Pages/DATRAS.aspx). Swept-area estimates were generated by ICES 2021ab (ICES. 2021a. Workshop on the production of swept-area estimates for all hauls in DATRAS for biodiversity assessments (WKSAE-DATRAS). ICES Scientific Reports. 3:74. https://doi.org/10.17895/ices.pub.8232; ICES. 2021b. Workshop on the production of abundance estimates for sensitive species (WKABSENS); ICES Scientific Reports. 3:96. https://doi.org/10.17895/ices.pub.8299).
ICES Data Centre host the database of trawl surveys (DATRAS) for groundfish and beam trawl data. DATRAS has an integrated quality check utility. All data, before entering the database, have to pass an extensive quality check. Despite this errors and missing data arise, which are subsequently dealt with by the data submitters from the contributing countries as required. However, this screening process was implemented in 2009 for data from 2004 onwards. Since some survey time-series extend back to the 1960s, historic data (unless re-evaluated and re-submitted by contributing countries) may not have been subject to the same level of quality control as these more recent data. Furthermore, the type of information collected, the level of detail and resolution in the data, has gradually evolved over time. In order to derive a single format, quality assured monitoring programme data product covering the entire Northeast Atlantic region inconsistencies in the datasets required resolution. These corrections are detailed in ICES 2021a,b: Biological data for trawl surveys are downloaded directly from DATRAS in raw exchange format (known as “HL data”). Ancillary data were processed by ICES 2021a,b to create the “SweptAreaAssessmentOutput” (which replaces the “HH data”) and these were downloaded from the same location: https://datras.ices.dk/Data_products/Download/Download_Data_public.aspx
Data are processed to create a standalone data product to be used for indicator assessments of fish and elasmobranchs.  Initially, hauls are subset to determine the Standard Monitoring Programme (i.e. excluding invalid hauls including those of duration shorter than 13 minutes or longer than 66 minutes, following Greenstreet and Moriarty 2017) and these hauls are used to define the Standard Survey Area by excluding areas sampled infrequently over time). Biological data were accepted with ICES SpecVal of 1, 4, 7, 10 (see http://vocab.ices.dk/ for further information on SpecVal categories). Additional QA/QC is made at this step to determine if species identification issues are present in the raw biological data and these were discussed and agreed with the Chief Scientist for each survey.