International Bottom Trawl Survey (IBTS) 1972-

Data set information

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Data holding centreSwedish University of Agricultural Sciences
CountrySweden  Sweden
Time period1972 - ongoing
Geographical area

Skagerrak, Kattegat


Fish taxonomy-related abundance per unit area of the bed; Fish taxonomy-related counts; Fishery characterisation; Fish and shellfish catch statistics


The ICES International Bottom Trawl Survey (IBTS) in the North Sea has been undertaken during January/February in each year since about 1970. Part of this survey includes station observations of hydrochemical measurements which has resulted in a most comprehensive dataset of the North Sea. The survey is conducted twice a year, one in the 1st quarter (15 days at sea, 45 trawl stations) and one in the 3rd quarter (15 days at sea, 45 trawl stations) with the research vessel ARGOS. The surveys cover area IIIa and are the Swedish part of the IBTS. The purpose is to estimate abundance by age, in particular for the recruiting year classes of target species (cod, haddock, whiting, herring, sprat, Norway pout, mackerel and plaice) in Kattegat and Skagerrak. Sampling of target species includes fish length, age, weight, sex and gonadal maturity and is carried out on board ARGOS. The otoliths are analyzed at IMR in Lysekil. Age determination takes place in accordance with standardised methods (Anon. 2000a). The sampling procedure and the level of precision are defined in the Manual for the International Bottom Trawl Surveys ICES CM 2000/D:07. The survey is ICES co-ordinated and performed in collaboration with research vessels from Denmark, Norway, Germany, Netherlands, England, Scotland and France. During the survey, a GOV bottom trawl is used at daytime. This gear is a standard and used by all countries involved. A Method Isaac Kidd trawl is used at night time in quarter 1 survey to estimate the abundance of fish larvae, in particular herring- and sprat larvae. Hydrographical data is collected with a CTD. Primary survey data are stored in a fish sample database administered by IMR in Lysekil. Aggregated data are reported and used annually by relevant ICES Working Groups. Since 1977, data are also stored in an internationally co-ordinated database at ICES in Copenhagen. Part of this survey includes station observations. Prior to 1993 the IBTS surveys were known as the International Young Fish survey (IYFS).

OriginatorsInstitute of Marine Research, The Swedish Board of Fisheries, FiV

Anon (2002) Report of The Baltic International Fish Survey Working GroupICES Headquarters 8 12 April 2002, ICES

Data web site
OrganisationSwedish University of Agricultural Sciences
AvailabilityBy negotiation
ContactJoakim Hjelm

Institute of Marine Research, The Swedish Board of Fisheries, FiV
Turistgatan 5, Box 4

SE-453 21

Telephone+46-(0)10-478 4021
Collating centreSwedish Meteorological and Hydrological Institute
Local identifier18004001
Global identifier77
Last revised2017-09-27