More (on) blue whiting - trawl 4-7

Over the past 2 days blue whiting continued to appear as soon as we were steaming over the shelf edge and continued until almost the end of our transect. The Irish seem to have observed something along these lines as well, as they even extended their last transect by 7 nm. The rule is if we are to still see blue whiting at the end of a transect we will have to continue until we haven’t seen any more blue whiting for at least 20 minutes.

Given the availability of fish, we are able to plan our trawls, in a way that we get relevant samples from the different areas, where we think differences in the composition could be expected. This is relevant as the occurrence of different length/age classes of blue whiting can be expected at defined bottom depth ranges. Generally along the shelf, at bottom depths below 1000m smaller fish are more likely to occur.

On a broader scale the survey itself is split up into 5 subareas:

I)             Porcupine

II)           Northwest Ireland

III)         West of Scotland

IV)          North of Scotland

V)           Rockall

Below a graph showing the length distribution of blue whiting caught in subarea II of the survey from 2006-2013, plotted against bottom depth. L15 and L20 (blue whiting of length 15 or 20 cm) are mainly caught at bottom depths <1000m, with only one haul presenting an exception, where large quantities of L15 and L20 were found further offshore. L25 and L30 seem to be well spread out over all bottom depths, while the bigger individuals are caught more rarely in this area. Bigger individuals are more frequently caught further North, in subarea III and IV.

 Just to continue with some information on blue whiting, for a lot of people it might seem strange that blue whiting is one of the most heavily fished species of the Northeast Atlantic but still it is rather difficult to find a restaurant which would serve it. In the Netherlands blue whiting is generally not sold for direct human consumption. They are a bit more popular in southern Europe and in Russia, but generally blue whiting is processed, either into fish meal, or pressed into fish fingers, Kibbeling or Surimi.

Back onboard the ship…

Lets start with the nice midnight snack Toni prepared for those of us working the night shifts...

We just took in our 7^th haul, which we took just a few meters above the bottom along the shelf edge (unlike the Norwegians, we have the right gear with us ;) ). As we fished along the bottom it is not very surprising that the catch besides blue whiting also contained some good sized hake.

The previous catches were all pure blue whiting trawls with very little mesopelagics. Trawl Nr 6 is worth mentioning as we hit a quite dense blue whiting school and hence were done rather quickly:

While trawling, Kinne our captain is carefully monitoring the sensors...

There is a good reason for everybody to be satisfied!

After the fish is caught it is taken on deck and pumped into the vessel

The next step is the sorting...

Laying the selected samples out by length classes

The measuring

And finally the identification and measurof the strange creatures of the deep

Where are the other ships? ...and some pictures

This is just a quick post with some nice pictures I was struggling to put in yesterdays post with the rather slow internet connection, coming along with an update on our location in relation to the other participating vessels. Twice a day, we are supposed to send an updated position to  shore, which allows Sascha, our land based cruise coordinator, to jump into action if one of us would rush away or be left behind. This generally would imply either a slight change of the cruise plan or the fastest vessel would have to wait for the other participants.

As you can see we are very nicely lined up at the moment, with Russia and the Netherlands looking as if they were part of a race, and just escaped from the Irish. Norway is currently surveying the Rockall area and is apparently surrounded by Russian fishing vessels, while they are observing a blue whiting carpet close to the bottom.
In the meantime 2 more hauls were done, but more about this a little bit later. And the Faeroe Islands started their part of the survey up in the north but their position remains as yet unknown... For now, enjoy some nice pictures taken during this trip so far..

First blue whiting, "good" weather and lost satellite

For the past days we couldn’t get our satellite connection to work properly, hence we did not have internet nor phone working on the vessel.

Luckily we managed to get it up and running again now and we are able to communicate with the outside world.

Since the last post the weather improved dramatically and we are now under the influence of a high, which leaves us “mild” North-eastern wind of “only” force 4-5.

During my last post I claimed that we would be calibrating in the Galway Bay prior to moving towards the beginning of the cruise track. Unfortunately, given the very rough weather conditions and the influence of a rather strong underwater current, we didn’t stand the slightest chance of executing a successful calibration, and gave up after a short period of time. As a consequence, we decided that during each CTD (app.  every 60 nm (~ 6 hours steaming)) we are going to check the functioning of the cables connecting the GPTs (General purpose transceivers) with the transducers on the towed body. If an error occurs, at least we might be able to point out exactly where and when troubles happened and could jump into action. At 5.15 (GMT) the next morning, we arrived at the beginning of our transect and started recording acoustic information.

First blue whiting 

Approaching the shelf and the Porcupine Bank, the first blue whiting marks kept showing up and we were able to see some trawlers on the radar. On Wednesday in the early morning we finally saw the first “real” blue whiting school.  The catch revealed it to be a pure blue whiting school (containing one hake, one mesopelagic shark (dogfish) and 5 mesopelagic species . The catch was dominated by 3-4 year old blue whiting. 

First haul

Second haul

Later on, while moving from Porcupine Bank down into deeper waters, we hit the next school and went fishing once more. The catch was very similar to the first one, with very little mesopelagics and a dominance by relatively young blue whiting.

On the echogram below besides a blue whiting school and our fishing exercise, relatively large pearlside schools can be observed above the blue whiting school.  It is striking how one can distinguish different layers on this echogram. A top layer with probably some plankton, followed by the pearlsides layer, under which probalby a mix of pearlsides and zooplankton mixed with various other stuff can be found. A bit further down the mesopelagic, or deep sea layer starts, containing the blue whiting school. Often such layers are indicative for the presence of a change in environmental conditions, like a thermocline, different light conditions, etc..

Further a ghost bottom (a copy of the real bottom, which is located at a greater depth, not visible on our recordings), and the shelf edge are indicated. If such a ghost bo

  

Second haul

Third haul

Later in the evening we passed over a truly massive school of more than 45 nm in length. As we already took 2 hauls early that day we did not intend to fish on it, but suddenly a rather strange picture developed on the echogram. Unsure if it might be blue whiting spreading out, fish predating on blue whiting or just something completely different, we shot the net once more…But once more it was a clean blue whiting catch with a lot of very small blue whiting (probably 2-3 year olds).

On the echogram the length and height are indicated. It should be noted that the start of this echogram coincides with the end of the echogram from haul 2. Hence bleu whiting was visible from the moment we went down the shelf, until we went it back up again.

Haul 3

For the rest we are currently enjoying the rather nice weather after we got shaken a bit at the beginning of the survey and are all happy that internet and telephone are up an running again. For now we like to believe the weather forecast, which predicts calm weather until Monday…which I think we would deserve after the troublesome start of the survey.