Winter Fieldwork: The North Sea and the Baltic Sea

The marine scientists of the University of Tartu are once again on a winter field expedition on the research vessel Walther Herwig III. On board from our team are Randel Kreitsberg and Ciara Baines. We document our experiences in a field diary and share photos and information about the daily life of a marine scientist.

Our work here focuses on fish cancer research, and the main purpose of this trip is to bring a number of live flounders to Estonia to test under controlled conditions (in a common-garden experiment) whether molecular defence mechanisms against cancer and pollution are effective also in changing environments – for example, whether fish continue to actively maintain their cellular defence when they are removed from the polluted environment into a clean one (further on our group’s activities see So we catch fish, collect samples, and furthermore bring them back alive to Estonia. This will be one very valuable fish cargo!

November 29. After testing for COVID-19 and waiting for the results, we were finally allowed on board the boat in the evening. We had a farmer’s breakfast for dinner (fried potatoes mixed with eggs), had to go through a series of formalities (safety instructions, ship briefing) and moved all the necessary research equipment to the various decks and cabins.

The top news of the day is of course the weather forecast for the next two days, which, to put it mildly… umm… will be wretched, sealike, Decemberish. The prediction for the coming days is up to 9 on the Beaufort scale, which stands for very strong wind and big waves. However, the captain says it’ll still be good enough to trawl the North Sea. We’ll let you know how it goes.

November 30. All of a sudden, I’m not feeling so good. Just 5 minutes ago I was proud of myself, happily humming (I certainly didn’t whistle, as whistling is not allowed on board) a tune and getting ready to have lunch, but now lunch is out of the question. It all happens in barely 2-3 minutes: seasickness knocks me off my feet, my arms and legs go limp and tingling, I have stomach cramps, throbbing neck pain, light is hurting my eyes. I crawl into my bunk and lie there, weak, arms and legs spread out, eyes closed.

I grab a packet of sweets from the shelf and eat a couple of toffee candies without opening my eyes. I start feeling better. I drink a little water, but not too much, fearing that if I had to pee, I wouldn’t make it to the toilet in time – or even if I made it, I probably wouldn’t make it back in time. I can hear someone vomiting next door and hearing it makes me sick. I close my eyes and try to get some sleep. I even manage to slip into a kind of liminal state between sleep and wakefulness. The dreams are strange and through my sleep I can feel the ship endlessly tossing me about. I’m trying to keep my back and neck muscles as relaxed as possible, but cannot fight the tossing around; also, otherwise I will suffer from cramps and sore muscles tomorrow.

Finally I fall into a deeper sleep. When I wake up, the ship is suspiciously quiet – people are lying down in their cabins, each struggling on their own – but also the ship doesn’t rock as much. Indeed, the captain has taken pity on us and we have found shelter from the storm behind the island of Helgoland. It gives no protection from the wind, however, so the gusts that sweep through the whole ship can be felt, but the waves are nearly gone compared to what they were. I’m feeling instantly better. The storm is over – at least for the moment.

I lift my head out of the bunkbed to look out the window. It’s getting darker outside. Still the same damned sea. A few clouds, the slightly pinkish horizon, the waves slowly receding. The same as before. I long for a spruce forest and snow crunching under my boots. Back home in Estonia, the snow is 15 cm deep and kids are already going to skiing practice. Luckily we won’t be trawling today, so we can relax for the rest of the evening. Tomorrow is another day.”

December 1. We must have had some kind of a hurricane here – called Daniel or Danielle or something. Beaufort force 11. We made two attempts at trawling today and are now we are back behind the Helgoland Island, sheltered from the waves. In the evening we’ll probably start moving through the Danish straits towards the Baltic Sea.

The small-spotted catshark of the North Sea

December 2–3. We’ve reached the Danish straits. We are about to cross the last big waves and the water is already calm east of the Jutland peninsula. It’s rather quiet on board, life follows a somewhat predictable path: the internet connection is bad, no meetings are allowed because of COVID-19 (a preventative measure imposed by the captain on our first week at sea) and so we just eat and sleep most of the time. Yesterday, the crew mess was decked with Christmas decorations: an artificial Christmas tree, a star light and some string lights.

The only research activity that night was taking some water samples from the deeper part of the Kattegat and testing an underwater unmanned vehicle. The Germans are also having problems with the internal information systems of the research apparatuses on the ship. Luckily, I have my laptop, field notebook and pencil – so as long as the fish can be caught, we’ll have everything we need for our research.

The food on board is authentically German. I’ve deliberately turned into a vegan here for a few meals – no one can eat all that processed meat and eggs and cabbage and potatoes and pasta and bread all the time. It is so nice when just for a change your entire meal is just grapefruit and vegetables and a glass of juice.

Tomorrow is an important day: we’ll reach the Kiel area in the morning and, after breakfast, we’ll catch our first fish from the polluted sea (where liver tumours are actively present in the local common dab population). Today we are making preparations for that, tagging sample containers and getting the equipment ready, and we have already calibrated the scales.

The crew mess. Once the restrictions imposed by the captain for a week are lifted, we’ll be having movie and board game nights here
Menu of the day. In addition to that, we are having a coffee break every day at 15, for which the cook bakes some pastry: butter biscuits, rum balls, sponge cake, etc.

December 4. Today was the first serious workday, during which we made 6 catches in total, starting at 7 in the morning and finishing at 19 in the evening. As I write this, my back and hands are tired and everyone smells/reeks of fish from head to toe. J Still, the overall motivation was high, even though we had almost no time to eat.

Fishing was done with bottom trawls in the sea and bay of Kiel, and the aim was to collect fish samples for several research projects. So we collected fish as bird food for a future seagull project, sampled flounders and common dabs, and measured and individually tagged 32 live flounders – to bring the latter back to Estonia alive in 1,000 litre tanks for a common-garden experiment and a series of different measurements. The aim is to see, for example, whether the pollution and cancer defence mechanisms of fish in the polluted Kiel area remain up-regulated even after a longer period of living in clean water (to distinguish permanent genetic adaptation from so-called temporary ones).

As for the fish, there were huge numbers of common dab and European plaice, with a few herrings, cods, turbots, flounders, and common soles. There were also some nice 10 kg cods. And, of course, lots of all kinds of starfish and shellfish. Tomorrow we’ll carry on in the same area. Fortunately, the sea is calm.

Good news on the house rules as well – the requirement of wearing masks and no congregating was dropped (following two rapid COVID-19 tests on board).

We took samples from ten flounders and common dabs
Helpers packing seagull food

December 5. For two days now we have hunted live flounder in the surroundings of Kiel. The crew is working overtime and even the captain drops in from time to time to ask how things are going, whether we’ve had enough already. J Anyway, it looks like we’ve infected the whole ship with “flounder fever”. Early at breakfast we start placing bets on how many flounders would be caught in the first trawl. I have to admit that my pessimistic 10 was more than doubled and today proved to be a much better day for flounder than yesterday. Anyway, we put in a good 11-hour day, and in two days we caught 127 live tagged fish from Kiel. This amount will do if you want to plan an experiment.

We are currently sailing along Germany’s north coast towards the island of Rügen, which is the next sampling location (compared to Kiel, the sea here is very clean and rich in fish, largely thanks to wind farms, or to be more precise, the no-traffic zone around them). The east wind has already kicked up a 3-metre wave by now – things are moving around on my cabin desk – and we are hoping that the fish don’t get seasick in the tank. All my clothes are impermeated with constant sea spray and a very specific smell. Maybe I should shave my beard… But there’s no rush. Luckily we have an ice-class vessel, so we’ll break through the young sea ice in Estonia when we get there at some point.

Placing bets: how many flounders we’ll catch in the first trawl
The standup meeting of researchers-students before pulling out each trawl. Pedro Nogueira from the Thünen Institute standing next to the map is in charge

December 6.  This morning we were surprised by Christmas elves. Some left chocolate at the door, others brought fish in the trawl. The very first trawl after breakfast gave us about 300 flounders, enough for both sampling and tagging live. After lunch, we held a big fish tagging event, asking people on the ship to help us, during which 162 flounders were tagged with a green personalised number on their ventral fin. The fish caught yesterday and today are feeling well and we are once again a little closer to home. With that, two research locations are completed, with the Polish coast and Hiiumaa Island still to go. Tomorrow we will be in Poland.

Today’s gift from Santa’s little helpers

December 7. Under Poland. We’re trawling fish. As there’s a little less flounder today, we’ll have to stay here for two days to get the fish we need. But there are plenty of cod. The weather is nice – today we went to the monkey island, the deck above the navigating bridge, to enjoy the view.

Evening mood. The final trawl of the evening resulted in a big catch of beautiful flounders (which, of course, meant that we had to summon people on board for another tagging event). We will be catching a few more fish in the morning and then we’ll leave Poland behind and head towards the Hiiumaa Island, navigating around the Russian maritime boundary.

December 8. The wind is picking up again. During the morning trawl we caught all the fish that we needed at the Polish sampling location. We are now heading towards Estonia, but the waves are high and it’s below freezing outside – the ship’s deck is covered in ice, with icicles hanging from the railing. The ship rocks so hard that a flounder flew out of the tank. We went out to rescue the fish and the tanks, to fix and set the covers. Everything is frozen and wet, water splashing around.

December 9. The sunrise in the morning is beautiful, but freezing cold. It’s also cold in the ship’s cargo hold, not to mention on the deck, which is completely covered in ice. The icicles on the railing are 30 cm long, and every time we go to check the health of the fish, the ship’s engine is stopped to ensure our safety and stability.

The weather in Estonia being so cold creates a serious problem. The four 1,000-litre tanks with fish on board have a constant overflow of seawater. And now this splashing overflow is constantly freezing into a several centimetres thick layer of ice, which covers all parts of the ship. The Germans keep building new systems – using all sorts of hoses and things – to protect the ship by keeping the ice from forming. And we keep dismantling them because the systems they build don’t work for us, they freeze, clog and endanger the health of the fish. So for the last two days we have been pulling a continuous tug-of-war: one side builds, the other side demolishes, and so far we have not found a good solution because the tools and equipment on board are also limited. In addition, all this has to be done in the dark, amidst several metres high waves, balancing on the ice covering the ship, hanging on tooth and nail.

Our first open-sea fishing trip off the coast of Hiiumaa yielded 28 flounders, a number of herring, Saduria entomon, a beautiful lumpfish and two shorthorn sculpins. After we had caught what we needed, we took samples and tagged the fish. The waves are high and the wind is strong. Estonia is not far from here, somewhere beyond the horizon.

We are tackling the massive logistics challenge to transport the live fish and four tonnes of water from the ship to the harbour and from the harbour to the laboratories at the Centre for Limnology.

It was a crazy day today, we finished work at half past 10 in the evening. Only one more day and a half of keeping the fish alive..

This is how marine research is done

December 10 and the following days. So much has happened in the past few days that I’m struggling to remember what we did on any specific day. What is certain is that we reached the Paljassaare Bay near Tallinn, the weather had warmed up and the icicles had started to melt. On December 11 we loaded the fish tanks off the ship. Well, not exactly off, but onto the port’s tender, which brought the precious fish, as well as me and Ciara, to the Port of Lahesuu in Tallinn. From there the fish tanks were loaded with the port crane to the truck and were on their way to the Centre for Limnology. It was quite a logistical challenge for someone who is doing it for the first time.

As we were leaving the ship, Ciara and I both admitted feeling a pang of sadness, as we had closely bonded with our colleagues and friends on board over the two weeks, and who knows if and when we will meet again. Lots of waving and hugging and good wishes were exchanged before we climbed down the rope ladder. People waving from the deck and the lights of Walther Herwig III once again disappearing beyond the horizon in the foggy Tallinn Bay. Another voyage had come to an end. It was a hell of a ride! 🙂

Photo credits: Randel Kreitsberg, Esther Wilhelm, Ciara Baines, Alexander Knorrn

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