First transects completed

The begin of the survey was occupied with the calibration of our echosounder equipment. For that we went to a sheltered fjord in southern Norway.



the towed body with acoustic transducers mounted in it

arrival in Kristiansand Bay, Norway



towed body in the water next to the ship, ready for calibration.

calibration beams connected to the towed body

the transceiver, heart of the echosounder

After calibration the survey started in the north of the area going along the predefined transects. Steaming at 10kts, acoustic sound waves are continuously sent out from the transducers in the towed body. The reflected echo from fish in the water is then measured and used to estimate the density of fish present.

If fish are detected by the echosounder we take a trawl sample for identification and length measurements. From herring we also determine their age, sex and maturity stage.

first herring samples coming on board

closer to the coast, some sandeel was caught as well.

another species regularly caught is mackerel, single individuals of which are usually present in surface waters.

Bram and HendrikJan measuring a herring catch

So far, we have completed the first five of the planned transects. These certainly represented the most 'busy' part of our area, where most of the herring is present. The folowing bubble plot gives an indication of the detected herring: the bigger the circle, the higher was the encountered herring density: