Publication on data.gouv.fr
Species and habitats - Clupea harengus - Mature - Mean abundance in October, standard deviation maps during CGFS (1988-2009)
Biologic data have been expressed in abundance (numbers or density values (nbr/km²)) and always required to be log-transformed using a log10(x+1) transformation. Abundance mean (mean) and standard deviation (st) have been calculated.
The survey extends from the Eastern English Channel to the south of the North Sea, which corresponds to ICES divisions VIId and IVc. The study area is divided into rectangles of 15¿ latitude and 15¿ longitude using a systematic sampling strategy. The sampling gear is a high opening bottom trawl well adapted for catching demersal species, with a 10 mm mesh size (side knot) for catching juveniles. This sampling gear is polyvalent and is well adapted to the varying seabed types encountered in the study area.One or two 30 minutes hauls are performed within each rectangle of the CGFS grid (two in the coastal zone and one offshore). The fishing hauls are chosen using professional fishing plans or found by prospecting. The fishing method is standardised: sampling stations have been each year at similar locations and identical sampling gear is used. Since 1997, temperature and salinity (surface and bottom) are measured using a probe attached on the headrope of the trawl. At each sampling…
Purpose: not specified