The integration was carried out with a 38 khz echosounder connected to a digital integrator. The units of acoustic reflection is area backscattering Sa m2/n.m.2 refered to 30 dB gain. The integration is carried out in predetermined depth channels down to 500 m. One channel is locked to the bottom. A sonar directed 90 degrees to the starboard side with a tilt of 5 degrees and a vertical range of 250 m were used to observe shoals close to the surface. The fish registration is identified mainly with pelagic trawling. In the case of shoals on the bottom catches of pelagic species in the bottom trawl were also used. A description of the pelagic trawl and trawl method applied in near surface or shallow water trawling is shown in Appendix 1. The additional buoyancy of the buoys allowed a warp length about 150 m without sinking tendency of the trawl. The longer warp length will give a better spread between the trawl doors and a better geometry of the trawl and thus an improved catchability. The aim is however to be able to tow the trawl more than 400 m behind the vessel at any depth to reduce the disturbance of the vessel. This could not be achieved with the available equipment.
The bottom trawl used for demersal trawling are shown in Appendix 2. The trawl stations are positioned in advance more or less randomly without using information from fishfinding systems. The standard trawling time is 30 minutes. The catch rates thus do not simulate those of commercial fishery.
The hydrografic sampling included salinity, temperature and oxygen at standard depths down to 500 meters.
