SISP 1 - Manual for the International Bottom Trawl Surveys

The International Bottom Trawl Survey Working Group (IBTSWG) coordinates fishery‐independent multi‐species bottom trawl surveys within the ICES area. These surveys aim to provide ICES assessment and science groups with consistent and standardized data for examining spatial and temporal changes in (a) the distribution and relative abundance of fish and fish assemblages; and (b) of the biological parameters of commercial fish species for stock assessment purposes.
In terms of groundfish surveys coordinated by IBTS, the main objectives are to:
1 ) To determine the distribution and relative abundance of pre‐recruits of the main commercial species with a view of deriving recruitment indices;
2 ) To monitor changes in the stocks of commercial fish species independently of commercial fisheries data;
3 ) To monitor the distribution and relative abundance of all fish species and selected invertebrates;
4 ) To collect data for the determination of biological parameters for selected species;
5 ) To collect hydrographical and environmental information;
6 ) To determine the abundance and distribution of late herring larvae (February North Sea survey).