Plattform Platform	Reise-Nr. Cruise-No.	Zeitraum Period	Projekt Project	Arbeitsgebiet Working area
Tridens II	wk 26-29/2011	27.06.2011 - 22.07.2011		North Sea

Fahrtleiter Chief Scientist	Institut Institute	Auslaufhafen Port of departure	Einlaufhafen Port of return	Stationskarte Station map	Schiffsroute Trackchart
Couperus Bram	Rijkswaterstaat, North Sea Directorate	Ymuiden	Ymuiden

Ziel der Reise / Objectives of Cruise:

After departure on Monday 28 June from the port of Scheveningen, Tridens steamed up in the direction of Scapa Flow. On 28 June at 56?25N-0?35E and at 56?25N - 0?35E test hauls were carried out. The calibration was carried out in Scapa Flow (Orkney`s) on 29 June. The conditions were insufficient for a successful calibration of the 200 kHz. For this frequency we uploaded the calibration settings from the previous year, but with a default gain of 27 decibel, 110 Watt (instead of 300) and a pulse duration of 1024us. The actual survey started on 29 June at 19.50 UTC. In the remaining days till the weekend stop in Aberdeen, 8 hauls were carried out. The survey was interrupted at 57?45N - 2?00W on 2 July at 6:22 UTC for the stop in Aberdeen. The survey continued on Monday 4 July according to the planned transects till Wednesday 6 July at 56?39N - 1?41E. Arrival in Scheveningen was on Thursday 7 July at 18:00 UTC. Departure from Scheveningen for the second part of the survey was on Monday 11 July. Tridens steamed up north-west to the start point of transect line 6 (56?20N-2?27W). While setting up and preparing the trawling gear and other equipment on the after deck, the CTD data cable got caught in another steel wire and snapped. This could be repaired by the IMARES technician. The network port in the wetlab turned out to be closed and no communication could be set up with the rest of the IMARES network. However, this was quickly resolved as the port managers were informed. The survey restarted on Tuesday 12 July at 08:00 UTC. During week 29 only one haul was carried out as fish were absent on most of the echosounder records. The weather turned to the worse during the week with force 7-8 winds. This caused some bad acoustic data due to the air bubble saturated surface layers. The survey was stopped on Friday 15 July after the end of transect 7 (55?39N - 1?27W) was reached and Tridens steamed to Newcastle-upon-Tyne for the week end break. Arrival in Newcastle was 14:00 UTC. Departure from Newcastle was on Monday morning, 18th July at 6:00 UTC. The survey continued on the same day at 08:55 UTC at the start of an additional transect that was introduced at latitude 55?24N between 1?27W and 1?41E. This was done in an attempt to collect additional biological data in the area. As enough time was available, this did not affect the original coverage. On 19 July at about 12:00 UTC, larger fish aggregations were detected by the echosounder. However, due to a defect cooling system, only one ship engine could be used and fishing was not possible. Trawl 11 revealed no fish catch, however, a white-beaked dolphin (Lagenorhynchus albirostris) was caught as bycatch. After organising transport, permits and freezer space, it was decided to bring it back to the Netherlands for further scientific examination by IMARES. The remaining transects were covered as planned until Thursday 21st July at 54?09N - 0?0E. ETA in Scheveningen was on Friday 23rd July at 06:00 UTC. Since 2010 cruiseleaders keep a weblog during the survey: http://www.imares.wur.nl/UK/publications/weblog/northseaherring/

Messungen / Measurements