Shortly after haul 21 this morning with the disappointing catch, we came across some nice clupeid pillars (= herring schools) off the coast near Hartlepool. We shot the net for haul 22 (54.47N - 0.46W) and managed to catch part of one off these schools.
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| During the trawl haul we made a full hit at a school. Hence the frequent "stickers" (Dutch: "stekers") in the meshes in front of the codend |
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The catch was one and a half ton of sprat (57%) and young herring (43%). The trawl sonar indicated that this mixed catch came from one school: apparently sprat and herring swim in mixed aggregations. This information is important for the interpretation of the echograms!
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| One and a half ton of sprat and herring in the hold of the vessel. |
In conclusion we have had a very smooth and successful survey with extremely good weather and much more herring in the Tridens-area compared to the previous five years. Our preliminary conclusion of this survey is that there is more herring in the area we covered. This does not mean that there is more herring overall in the North Sea. It may indicate that the distribution of herring in the North Sea was different. At home - IMARES in IJmuiden - we will analyse our data. Next January, during an
ICES Working Group meeting we will combine our data with those of the other participating countries in this survey in order to make a combined estimate of the abundance and distribution of herring (and sprat) in numbers and biomass.
The last version of the bubble plot showing the acoustic density of herring (up until yesterday evening) can be seen below:
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