Once More into the Breach

Welcome to the webblog for the Dutch contribution to the International Blue Whiting Spawning Stock Survey 2016, an international collaboration between Norway, the Faroese Islands and several EU countries. Unfortunately, Russia is not participating in this year's survey. 
 
We are aboard the RV Tridens, which departed from Galway in the early hours on Monday 21st of March. You can track the vessel here:

https://www.vesselfinder.com/vessels/TRIDENS-IMO-8821852-MMSI-244033000

The seas were remarkably calm throughout Monday. We reached our first station (GPS position at which we begin our transect or take measurements), near the continental shelf edge at the Porcupine Bank, at about 7 p.m. and began the acoustic transect work. Here is an example of an echogram we recorded.



Acoustics is a scientific means of detecting and measuring the changes of density in a medium (in this case sea water) using sound. Since fish are more dense than water, they are readily distinguished in the water column. It makes for a powerful, non-invasive method to estimate stock abundance and biomass of large schools of fish. To verify the acoustic readings, we will be doing fishery analysis via trawl net. 

In the meantime, we had a look at the local birds. They were predominantly gannets, black-headed gulls, fulmars and a few blackbacked gulls.  



The sea is a little rougher today with an area of low pressure coming towards us. 

 









We are currently about three quarters into our second transect, no sight of large whiting schools yet, hopefully this evening. Lots of sea to cover.  

It begins: Blue Whiting Survey 2015

Unfortunately I was unable to upload yesterday’s blog, so here it is today:

Yesterday (Monday 23^rd March) we departed sunny Galway harbour and headed towards the first destination on our newly appointed cruise track. ‘New’ because of a last minute swap with the Russian vessel, ‘Fridtjof Nansen’ due to some issues over their entry into British waters. The seas have been rougher than expected during Monday evening/night which meant we arrived at the first transect several hours later than expected. 

New cruise track for the Tridens.

To our destination.

Despite being well prepared and having done a good calibration of (most) transducers during the test weeks prior to the survey, bad weather has meant large(ish) waves have been continually crashing onto the bow of the Tridens, which resonate sound through the hull. This sound is easily picked up by the echosounders. When you stand in the drop keel room you can hear large crashes and bangs - these are seen as hard spikes on the echograms. We tried a few tricks to hopefully reduce the interference; including a range of speeds and depths to which the drop keel was lowered, unfortunately these made little difference. Lowering the bow of the ship did however reduce the interference slightly. 

Teething problems. Newly installed drop keel aboard the Tridens.

Scientists sharing concerns.

Print screen of 38 kHz echosounder showing 'noise' caused by crashing waves on the bow of the Tridens.

All newly installed equipment is prone to teething problems and aboard the Tridens there is no exception. The main resolve will be to hope for better weather before we come across the main aggregations of fish further along the cruise track (fingers crossed!).