Blog post

Last transect & additional zig-zag

Published on
April 11, 2012

We finished the last transect of the official survey track on 09.04. at 22:22 GMT.

Shortly before that, we just crossed the border on the shelf edge again and came across some blue whiting at 58º12.3’N 9º20’W:
trawl14.png

Since we made good progress throughout the survey and had some additional time available, the decision was made to extend the covered area further north. To cover the shelf edge northwards, we progressed in a zig-zag design between bottom depths of 200 and 1000 m:

zigzag.png

The presence of the commercial fleet in the area was already a sign that we may come across some bigger aggregations there. This turned out to be the case. Here a few example echograms from the area:

Sampling such aggregations was rather easy, since the fish are in long layers at a constant depth. Here a couple of example images from the netsonde or trawl sonar – it is located at the top of the net entrance and basically monitors the catch going into the net. Blue whiting schools can be seen entering the net (rectangular object):

Fishing on these aggregations revealed almost clear blue whiting.

At the bottom of the shelf edge, we again sampled the mesopelagic community in an attempt to get a better picture of the whole ecosystem. This involved painstaking work to separate and identify some more deep sea fish:

Sharon Sheehan, an observer contracted by the Irish Marine Institute, spent some of her time on board keeping a look out for any marine mammals in the survey area.