North Sea, sampling depending on international coverage

Fish morphology, age and physiology; Fish taxonomy-related abundance per unit area of the bed; Salinity of the water column; Temperature of the water column; Raw temperature and/or salinity instrument output; Fish taxonomy-related counts

Plankton nets; balances and scales; rulers; CTD; demersal trawl nets

The North Sea International Bottom Trawl Survey is carried out with an otter trawl (20 mm mesh in the cod-end).The main objective of the IBTS is to provide fisheries-independent recruitment indices of these commercial fish species. Furthermore, to get an early indication of the potential amount of young herring, the abundance and distribution of herring larvae is monitored by fishing with a plankton net at night. The IBTS targets the following commercial finfish species: herring (Clupea harengus), cod (Gadus morhua), whiting (Merlangius merlangus), haddock (Melanogrammus aeglefinus), saithe (Pollachius virens), Norway pout (Trisopterus esmarki), mackerel (Scomber scombrus), and sprat (Sprattus sprattus). However, all species are sorted from the catch, fish are measured and counted, other species are counted and weighed. For species of commercial interest biological information is collected following a stratification. The IBTS indices are used by the ICES Working Group on the Assessment of Demersal Stocks in the North Sea and Skagerrak (WGNSSK) and the ICES Herring Assessment Working group (HAWG). The IBTS also contributes valuable information concerning the state of the North Sea ecosystem, and used for the North Sea ecosystem assessment. Parallel to trawling, hydrographic data (salinity, temperature) are collected. The survey is part of the EU Data Collection Framework and internationally coordinated by the ICES working group on International Bottom Trawl Surveys (IBTSWG).

Http://doi.org/10.17895/ices.pub.5713 (2019) Manual for the International Bottom Trawl Surveys, SISP 10, ICES

Wageningen Marine Research, IJmuiden
Haringkade 1
IJmuiden

1976 CP
Netherlands