Sprat off Hartlepool and conclusion

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.

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

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!

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:

Porbeagle!

Yesterday - another beautiful day - in the morning (6:30 UTC) we shot the net at 55.25N - 1.28E for a few comparatively large schools in an otherwise empty area (haul 19). The schools were not easy to catch but eventually we hit one. When the net was being hauled something big seemed to stick in the codend.

The crew noticed something in the codend

It turned out to be a large specimen of a porbeagle (in Dutch "Haringhaai"). She (yes, it was a she!) was still very much alive and the crew released her as carefully as possible - not easy with a fighting shark of this size!

We estimated the length of the porbeagle at 2.80m!

Apart from this one large predator the catch consisted of 1.3 ton of young herring (Dutch: "toters") , length range17.5 to 22cm.

Also in the catch: squid (Loligo forbesi)

...and two lumpsuckers!

In the evening, we encountered a lot of small schools at the bottom. They were really difficult to catch. In the end, after one and a half hours trying, we hauled the net for a few baskets of young herring (similar to the herring in the haul in the morning) scattered with some adult specimens (haul 20, 54.24N - 0.20E).

Small schools at the bottom (haul 20)

Cannot wait to join spawning: One male specimen of 20.5cm has already a ripening gonad!

This morning, wednesday 17 july, the net is shot at 54.55N - 0.36W for what we judge to be herring that not yet is grouped into schools. The idea is to fish them now instead of waiting till they lump together: schooling herring is more difficult to fish (haul21).

Scattered swimming herring(?) in haul 21.

The catch is very disappointing: 7 specimens of sprat and one whiting...

BBQ and the blues upon the river Tyne

Saturday 13 July, 13:30, we finished the second of the two longest transects of this survey and headed for a stop in Newcastle. While we sail upon the river Tyne towards Newcastle, we meet an old acquaintance: "our" own ferry which we see daily in IJmuiden where our department of IMARES is located.

The DFDS ferry Newcastle - IJmuiden

Kittiwakes in Newcastle build their nests in windows, on bridges, roofs etc. During our stay, we can hear them all the time. The sound these birds make is supposed to be "kittiwake", but I am not sure whether everyone agrees on this.

Nests of Kittiwakes in the ridges of these factory buildings.

Saturday evening part of the scientific crew went to the pub, studying local ales, stout and cider brands: research is deeply settled in our genes! In the pub we met Tim and Jenny from Birmingham and Newcastle respectively (Tim is Dutch!). Immediately they were invited for our barbeque the next day. Fortunately the weather was beautiful!!!

From left to right: Arie (engineer), Dirk (our man from Havana), Sascha, Jenny and Tim

Overview of the barbeque on the front deck of Tridens.

 After the BBQ we went to the Tyne bar, where the yearly blues festival was going on.

The blues festival at the Tyne Bar was attended by some mysterious looking persons (sea uttermost to the right: Che Guevara??)

 Newcastle is relatively bike-friendly. Like in the Netherlands there are special parking lots for bikes. The difference with the Netherlands is that in Britain, a special P-sign with a bike-icon is required in order to let people know what these steel things are meant for!

Parking spot for bikes.

The Lyndon Anderson Band at the Tyne's bar blues festival.

 O yes, fisheries research: Monday morning we left Newcastle to start on the 55.25 N transect in eastern direction. Just east of the Farn Deeps, we shot the net for these interesting mark on the echogram. They were much stronger on the higher freqencies than on the 38 kHz, indicating that this may be something without a swimbladder. The catch revealed large quantities of Northern Krill (Meganyctiphanes norvegicus), some whiting, on specimen of sprat and some very small (2-4cm) norway pout and cod.

 

Northern Krill (Meganyctiphanes norvegicus) and whiting.

Northern Krill is an important food species for a lot of fish species, birds and cetaceans.

Meanwhile on board, in our hydro acoustic room a butterfly was caught in the light of the window. As we are working on our ecological profile continuously, we looked up the species and made a record here: Ringlet (Aphantopus hyperantus), in Dutch "Koevinkje".

Ringlet or (in Dutch) "Koevinkje"

Tomorrow we hope to encounter again some herring.

A message from above

Also on board of Tridens is ornithlogist Tim Sykes. Tim is counting seabirds and cetaceans according to an international accepted protocol developed by European Seabirds at Sea (ESAS). He sits in an observerbox which is fixed on top of the bridge. Probably he is more grateful for the nice weather than anyone on board. 



Tim at work in the 'observer box' on top of the bridge of Tridens



“There’s something mesmerising about watching the sea from a moving vessel.  Just as well really, when so much of the North Sea is seemingly devoid of visible wildlife!  I’m on board the RV Tridens to survey for seabirds and marine mammals, and it’s quite amazing to cover mile after nautical mile of potential wildlife habitat without actually recording anything.  But, sooner or later, you know you’ll come across a ‘hot-spot’ and the feeding activity can become frantic; it can be challenging to even write everything down quickly enough!





Fulmars become clumpsy under windless conditions.



At this time of year, our seabirds in Europe are all foraging out at sea to find food for their chicks back at the colonies on land.  Most noticeable on this survey, are the gannets, fulmars, kittiwakes and other gulls, and auks too (guillemots, razorbills and puffins).  A few other species have been encountered also, having wandered a bit further from their breeding grounds than normal – great skuas, manx shearwaters, and storm petrels.



Great Skua's amongs fulmars in the wake of the vessel.



For others though, the breeding season is drawing to a close already: whilst the first few guillemot chicks are already swimming out to sea, we’ve also encountered two ‘land-birds’ on the boat this week, in the form of a collared dove and a common crossbill!  In a way it’s sad to think that, whilst we humans are still enjoying mid-summer, these birds are already moving into position for the winter months ahead.



White-beaked dolphin



Minke whale



We’ve also had a measure of excitement in mammalian form, as minke whales are just starting to move north through this area, and white-beaked dolphins too are in evidence.  The latter have been making their presence known on occasion by performing spectacular acrobatic leaps, and in the right conditions can be seen at a distance of up to 8km away!



I always think it’s worth enduring the quiet times out here, as the busy times can offer such amazing wildlife encounters which are very rarely seen from dry land!"

Pictures by Tim Sykes.



Grey seal





Fulmar



More herring at the 'Devil's Hole'!

Today we were passing the Devil's Hole area on the 6th transect going east. After a few medium-sized aggregations of herring, the echogram was soon dominated by a few large schools:

 

The net was shot soon after at 56º25'N 0º13'W to take biological samples of these herring. The result was a reasonably big catch:

 

Rob guiding the catch safely on board A gannet observing the net from the sea surface Diving gannet going for some herring

the catch contained several tons of clean herring thereafter it was again up to Bram and HendrikJan to take the measurements

this shows some sprat that was caught in another haul earlier that day close to the coast

 

 

First transects completed

The begin of the survey was occupied with the calibration of our echosounder equipment. For that we went to a sheltered fjord in southern Norway.



the towed body with acoustic transducers mounted in it

arrival in Kristiansand Bay, Norway



towed body in the water next to the ship, ready for calibration.

calibration beams connected to the towed body

the transceiver, heart of the echosounder

After calibration the survey started in the north of the area going along the predefined transects. Steaming at 10kts, acoustic sound waves are continuously sent out from the transducers in the towed body. The reflected echo from fish in the water is then measured and used to estimate the density of fish present.

If fish are detected by the echosounder we take a trawl sample for identification and length measurements. From herring we also determine their age, sex and maturity stage.

first herring samples coming on board

closer to the coast, some sandeel was caught as well.

another species regularly caught is mackerel, single individuals of which are usually present in surface waters.

Bram and HendrikJan measuring a herring catch

So far, we have completed the first five of the planned transects. These certainly represented the most 'busy' part of our area, where most of the herring is present. The folowing bubble plot gives an indication of the detected herring: the bigger the circle, the higher was the encountered herring density: