Data on fish stocks, Nephrops Functional Units, fishing effort and catches by fleet and sale price data were used in a multifleet, mulitstock model (FLBEIA). Inputs on fish stocks were obtained from the ICES Working Group on the Assessment of Demersal Stocks in the North Sea and Skagerrak (WGNSSK) which follows standard, validated stock assessment methods.
Data on fleet effort and catches were obtained from the Scientific, Technical and Economic Committee for Fisheries (STECF) data portal. STECF presents discards as they are submitted by each nation and no longer applies its own discard raising/fill-in procedure. Therefore, a discard raising procedure was needed here. Discards were raised by calculating the mean discard rate by year, area and species, and applying the rate to landings records that did not have any corresponding discard information. As a quality check, the total discards estimated from the STECF data for each stock were compared to the total discards reported by WGNSSK where some substantial discrepancies were revealed. The source of these discrepancies was found to be some discard estimates flagged as poor quality by STECF. To resolve these discrepancies, these poor quality estimates were removed and the mean discard rates were recalculated.
Sale price information by year and stock was obtained for Scottish vessels only from the Marine Directorate Fisheries Information Network / iFish databases. Information on fishing gear type in the sale price data were converted to STECF gear types according to standard procedures which have been in operation at MD for many years to then derive mean sale prices by year, fleet, stock etc.
The methods used to define fleets, derive parameters and condition the fleet dynamics in the FLBEIA model followed the standard procedures developed and used for many years by the ICES Working Group on Mixed Fisheries Advice.