St Kilda, Calibrating and finally some nice weather

FINALLY SOME NICE WEATHER!

Yesterday we had to go to St Kilda, in order to wait for the other two participating vessels, because they were a bit too far behind us.
For the blue whiting survey, it is important that all the vessels stay in close proximity to each other, so that we can use the data in the end and realise and the best possible synoptic coverage. In the end we had to chose if we want to continue sailing with 6 knots or go to St Kilda, which was only approximately 1 hour steaming away from us, to let the Irish and Russian come closer to us again. Sailing with 6 miles is not the ideal solution for us though, as we are using a towed body, which will tilt at a certain angle under the water surface if we do not survey at approximately 10 knots. Hence we decided to sail to St Kilda and reschedule the calibration which was planned for after the trip. While the calibration prior to the survey did not work out too well due to harsh conditions, it went very well this time.
The video below shows you how we set up our calibration equipment:

The picture below is an underwater shot of the towed body

 The red circles at the bottom of the towed body are our transducers, the bigger circle is the 38kHz and the smaller one the 120 kHz. On the picture below you can see the towed body hanging along the ship.

 While Eric, Kees, Thomas, Dirk, myself and most of the crew were calibrating, the others went for a small boat trip into a cave, where they could observe a lot of seals and made a few steps onshore, walking up a hill...

TRAWL 9
After the calibration we went straight back to our "business as usual" - surveying...
Back on track, it wasn't for long until we saw the first schools coming up again. We realised another pure blue whiting trawl yesterday late in the evening.

Impressive catch on Tridens

Sometimes you can really be surprised from what kind of creatures you bring up from the deep. Today we had such a moment, the entire crew and all the scientists on board were astonished when we took in our haul this afternoon. We did not see too much fish coming in on the trawl sonars but suddenly the catch sensors announced that the nets were full. When the net came in we found this giant deep sea squid (Todarodes magnaiocus). More on this topic to come as we get some more information about the species and a positive response about its correct identification from the experts back onshore. So for now enjoy a snapshot of our impressive catch!!!

Keep on riding the waves

We are still on track riding the waves, with a continuous wind-force 8 blowing from the southeast. Luckily enough we managed to keep on with our survey work without too many interruptions. Tomorrow or the day afterwards we should finally enter the high pressure area and finally get some nice weather.

Since our last post we did a couple of more trawls which gives us a total of 8 trawls now. After the fifth trawl, our net broke and the crew had to work the entire night to get it fixed again. They did a great job and we were ready to shoot the net the again next morning.

All 3 catches were pure blue whiting trawls, always mixed up with some mesopelagics.

Trawl 6

Trawl 7

Trawl 8

Trawl 9

Our latest trawl was aborted because we had some problems with the winch which we are trying to fix right now...

For those of you who wonder how blue whiting looks like on the conveyor belt have a look at this video:

  

To get an impression of how it looks out here, have a look at the following video which Matthias recorded with his camera mounted above the bridge. As we have winds blowing from the southeast the swell is not too high out here, because it doesn't build up over a vast space as it would, if we would have the "usual" westerly winds. Still wind-force 8 - 9 is strong enough...

 

 Another experiment we did during one of the trawls, was to mount the GoPro camera on a five meter pole and lower it into the water, to have a look at diving gannets, here some frist results, more footage to come as soon as we hiot some nicer weather and do not have to be scared to loose the camera anymore...

TRIDENS defeats the weather

 The predictions of yesterday became obviously true and we faced wind force 8 for the entire day. Looking at the weather reports, it seems like we are going to be stuck with this kind of weather for the next few days at least...

These harsh weather conditions let our Russian and Irish colleagues struggle a bit, with the Russians facing even more severe conditions further out west, hit badly by the low pressure and the Irish not able to fish in these conditions. 

Nonetheless we saw some nice blue whiting schools today...And we fished on it!...Twice..

Trawl No 4:Trawl No 4 was a pure blue whiting catch, executed last night with some mesopelagics..

Trawl No 5
Trawl No 5 was again a pure blue whiting catch with very few mesopelagics, a few squids and a dealfish.

Left: Dirk having a serious look at the blue whiting               Right: Jeroen and James going through the mesopelagics and squids 

    Squid caught during trawl No 5

Third trawl and change of the cruise track

For the third trawl of this cruise we set out the net, mainly because we couldn’t agree on what kind of fish would be sitting there at the bottom (see echogram below).
Every time we pass the shelf edge we see those kind of bottom pillows before the typical blue whiting snakes are rising.The only thing most of us were convinced of was that it would not be blue whiting…
To our surprise, the catch turned out to be a mix of mainly blue whiting, silver smelt, mackerel, some hake, a grey gurnard and a few mesopelagics. More or less the North Atlantic platter…
  


The weather predicts gale warnings from south-eastern direction, so we decided to cut short our current transect a bit, in order to get North quicker and avoid the risk of loosing to much time out in the far West… With such weather conditions, we always run into the risk of not being able to use the acoustic data and not being able to fish…

To finish this post, a few pictures taken while hauling the net:

 

First 2 hauls and new storm warnings

We saw our first blue whiting marks on the echograms. The schools are not extremely big yet, but we wouldn’t expect them to be so in this southern part of the survey at this time of the year. We should hit the big stuff further North at around 56° North, just west of the shelf.

We do fishing, to ground truth our acoustic findings and to collect biological samples. 250 fishes are measured and weighted, from which we produce length-weight and length frequency relationships. Additionally 100 otoliths are read. Otoliths are the hearing stones of fish. They can be used to read the age of the fish, using similar methods as known to most of us from dendrochronology, or in other words, tree ageing. Put in simple words, we have to count the rings. This is a relatively difficult job as these stones are very small and have to be read under a microscope.

About the weather forecast…We can still claim to be fairly lucky with the weather up to now, given we are out on the Atlantic by the end of March. If we believe the weather forecasts, we should get into wind force 8 tomorrow and on Friday, which I would describe as being at least sub-ideal conditions…

Trawl 1

Time: 11:47 (UTC)
Position: 53°47' N    13°57'W

We hit the school quiet hard and got 5 tons of blue whiting in the net. It was what we would call a clean blue whiting catch containing nothing but blue whiting, 1 dealfish and 10 myctophids.

 Blue whiting school we targeted for haul number 1, as seen on the 38 kHz echosounder:

Trawl 2

TIme: 21:53 (UTC)
Position: 53°58' N    12°58' W

In the second catch we got up 2 tons, again pure blue whiting with 2 dealfishes, 2 squids and a few mesopelagics.

Blue whiting school we targeted for haul number 2, as seen on the 38 kHz echosounder:

Start of the survey

After the weekend stop in Galway we hit the ocean and are now waiting for the first blue whiting schools to show up.
TRIDENS reached the official starting point of the survey yesterday evening at around 3 o’clock. For now Posseidon is still relatively friendly to us, but if we believe the weather predictions, we are due for some heavy winds on Friday

Our German colleague Matthias Schaber brought his nice GoPro camera and recorded our departure:

Calibration with gale warnings

Prior to the weekend stop in Galway the acoustic equipment has been calibrated in the Bantry Bay. Due to relatively strong winds (gale warnings), calibrating was a rather difficult task. We managed to get an acceptable calibration out of it for the most important echosounder (38 kHz), but unfortunately we couldn’t calibrate the 120 kHz. Luckily we will have a second chance during the post-calibration planned to take place in Loch Eriboll at the end of the trip.

Leaving the harbour and gale warnings

Tridens left the harbour yesterday morning in Scheveningen, heading towards Bantry Bay in Ireland.

In the Bantry Bay we will be carrying out a calibration of our acoustic equipment, which is needed to check the correct functioning of the equipment. As soon as the calibration is done, we are ready to steam towards Galway, spend the weekend onshore before we start the "real" survey.

The picture above shows our planned cruise track (orange line).
 More details on the survey will follow soon, but up to now it seems like we are going to hit some rough weather...

Survey Blauwe Wijting 2013 op 19 maart van start!

Onderzoekers van IMARES Wageningen UR varen van 19 maart tot 12 april 2013 weer mee op onderzoekschip de Tridens en zullen in deze periode het Nederlandse deel van de internationale survey voor blauwe wijting uitvoeren.
Het gebied wordt bevaren via een vooraf bepaalde systematische route, waardoor de stand blauwe wijting door de onderzoekers goed in kaart kan worden gebracht.

Lees meer op: http://www.wageningenur.nl/en/Expertise-Services/Research-Institutes/Weblogs/Survey-Blue-Whiting.htm