in Greenland seas


Walther Herwig III, sea blog of the 410th cruise

Duration: October 6 to November 21, 2017

Survey area: North Atlantic

Purpose: Abundance estimations of demersal fish species (especially cod and redfish) and oceanographic/climatologic investigations in Greenland waters

Objectives and map

Seit 1982 wird die West- und Ostküste von Grönland jährlich nach einem standardisierten Fangprogramm beprobt. Das Untersuchungsgebiet ist in 14 Strata unterteilt. Die jeweils erste Nummer der Strata-Bezeichnungen gibt die geografische Lage an, die zweite Nummer die Fangtiefe (1 = 0-200 Meter; 2 = 201-400 Meter) (© Thünen-Institut)

The research programme of the 410th cruise incorporates fisheries biological investigations of the cod and redfish stocks as well as other ecologically important demersal species in Greenland waters. Beyond these abundance estimations, zooplankton will be collected in East Greenland and oceanographic data taken every morning and evening.

Cruise leader: Karl-Michael Werner, Thünen Institute of Sea Fisheries

After storm „Xavier“, which devastated the North of Germany and brought a couple of stormy days for us on board in the southern North Sea, the preparations for the lab work have now started. These mainly consist of labelling and sorting a variety of containers and jars, which have to be ready for use when the scientific sampling has started.

Another main part of these preparations are also safety instructions for working in the lab and the use of chemicals, such as ethanol or liquid nitrogen. Equally important before the first samples come on board is that the scientific staff on board gets to know each other to organize well-structured working routines for the lab. First bottom-trawl samples will be taken in East Greenland in a few days. In order to ensure a smooth and successful start, scientific staff is divided into smaller sampling-units, which are now preparing themselves for their specific jobs in the lab. As part of these different sampling-units, we will take liver and gonad samples for lipid analyses, finclips for genetic stock identification, and stomachs for trophic investigations this year.

The atmosphere on board is fantastic and everybody is looking forward to the first hauls coming on board.

With best regards
Karl-Michael Werner (Cruise leader)

The last days of the first survey week are dominated by a heavy storm. After a smooth crossing of the North Sea we are now waiting in northern Scotland, in the North of the Moray Firth, for a storm between Iceland and Scotland to pass. Crossing the North Atlantic from Scotland to Iceland takes approximately 2 days, but would not be possible under current weather conditions with 9-10 m high waves.

However, although scientific sampling has not started, boredom has not emerged yet. During a first aid workshop, the medical doctor on board, Dr. Norbert Jaeger, who also works as emergency doctor, taught us many valuable and helpful skills, which might be needed during a potential case of emergency.  Captain Stefan Meier offered a guided tour on the bridge, which provided new insight into the everyday life of the nautical officers.

In the meantime, life on board mainly consists of fine-tuning lab work routines in order to ensure a smooth and successful transition into scientific sampling. Despite of the storm break, the atmosphere is still fantastic and everybody is looking forward to get their hands dirty when the first samples are taken.

After the storm between Scotland and Iceland had passed, the Walther Herwig continued its voyage towards Greenland at October 14th. We steamed with low speed from the northern part of Scotland through Pentland Firth, the strait between Scottish mainland and the Orkney Islands, towards the open North Atlantic. With wave heights of up to 8 m, regular work on board was still not possible for us scientists. While some were fighting seasickness, others continued preparations for the lab work.

After two days, when the sea had calmed down, the first whale and dolphin sightings were made, what positively affected the scientists’ mood after the storm break. Yesterday, at October 16th, sunrays kiss the boat for the first time after several days of bad weather, while the ship is heading straight towards Iceland. Currently, the ship is waiting in the bay of Reykjavik for another storm to pass. Weather conditions over the North Atlantic do not allow any scientific sampling now.

Finally, after a stormbreak of two weeks, the first hauls with several tons of cod and redfish came on board on October 21st. As part of the standard sampling protocol on board, the scientific staff takes length, weight, sex and maturity of individual cod. Additionally, otoliths are taken for age determination later in the lab. Similar to trees, which have annual growth rings, the age of fish is determined with the number of rings in an otolith. The calculation of an abundance index is one of the main objectives of the survey. We want to answer the question: “How much cod and redfish is there in Greenlandic waters?”

Especially important for this abundance index is the age composition of the stock. Mortality in fish is usually highest during the first year. Only a tiny fraction of the initial number of eggs survives and grows to maturity. This interannual variability of mortality in the early live stages is reflected in the stock several years later, when certain age classes with comparably lower larval mortality are dominant. Determining the age composition is thus an essential part of a sustainable exploitation of a fish stock.

Another two days of storm break occurred after the first successful days of fishing, where we collected a lot of valuable samples and data. In order to escape a predicted storm in the Dohrn- and Gauss Bank area, we steamed 150 nautical miles southwestwards to Fylkir Bank, where wind forces of 5-6 were predicted, what would have allowed us to work. In contrast to the weather forecast, the rising storm over East Greenland brought wind forces of 9-10 into the Fylkir Bank area and made scientific work impossible. During autumn research cruises in Greenland good and bad lie often closely together; while one day brings weather with optimal working conditions and dolphin sightings, the other day can make scientific sampling impossible and life on board hard.

However, today at the 25th of October, the weather is fantastic and conditions optimal. Scientific work is going full speed and the atmosphere on board much better again. The weather forecast for the next days predicts stable conditions and we are all hoping to be able to work non-stop for several days.

For the first time on this survey, we were able to fish for three days non-stop. After very inconstant weather conditions at the beginning of our journey, we are now able to systematically sample the fish stocks in East Greenland. In order to fulfil the main objective of the survey, which is the calculation of an abundance index for cod and redfish, it is important to sample as many stations as possible. The calculation of this index is fairly simple; one knows the number of fish in a certain area and can extrapolate this number to the total size of the area. Fish stocks are rarely equally distributed in space. Often, large density gradients occur. Having many stations with a detailed overview of these density gradients is extremely important for a precise calculation of the stock size. After the survey, we send this index to ICES, the international council for the exploration of the sea, where it is used to provide the scientific catch advice, an essential tool for the sustainable exploitation of our marine environment.

After being able to fish non-stop for several days, it is not the first time that our work is interrupted by a heavy storm. Despite of the upcoming bad weather, we are able to bring the first Plankton hauls on small Bank, a fishing ground in East Greenland, on board. Plankton catches are made during the night, because many Zooplankton species migrate vertically up in the water column when it gets dark. The samples will later be analysed by Katharina Koschmieder, a Master’s student from the University of Hamburg. For her thesis, she will look at the Zooplankton species composition in East Greenland. These plankton data have been collected for several years. Samples are taken with a “Helgoländer Ringtrawl”, a typical net for the collection of Plankton, which is towed behind the ship.

In order to escape the upcoming storm, Walther Herwig III steams from small Bank to Qaqortoq afterwards. With its 3000 citizens, Qaqortoq is the centre of South Greenland. Here we also get fuel for the ship, we will need later for the journey back to Germany.

Visiting a harbour is essential for the boat; fuel and food has to be stocked up. Going on land in the city of Qaqortoq was the first time for many cruise participants on Greenlandic mainland. Eva Abraham, part of the scientific crew, describes her first impressions of the city in southwest Greenland:

“Sun is rising over beautiful Qaqortoq – or, well, at least some light sheds through the dense clouds. Colorful houses scatter the surrounding hills. We're eager to finally touch some ground. Descending the gangway, we make our way past the tiny market – here, the wale catch of the day is advertised – we pass the town fountain to climb up wooden stairs and later bare rock to reach the top of the city peak for a marvelous view over Qaqortoq – with its 3000 inhabitants it forms the biggest settlement in the south and the 4th largest of entire Greenland. Looking down we can spot Walther Herwig 3 hanging out at the pier and an ice-blue iceberg making its way into the photo. Turning around there lies a breathtaking fjord panorama. It smells of lichens, moss and wet stone – the rock formations being one of the oldest on this planet, they are up to 4.5 billion years old, unbelievable really.

But duty calls – at one o'clock sharp we're standing in Hentzar Petersen's fish factory. Well equipped with hairnets and work coats we enjoy an informative tour of the factory and listen to the fisheries stories of our Faroese guide. He owns two other factories in the east of Greenland. Bit by bit we get our heads around the importance of fishing in this area. This gets even clearer as we enter the town hall and are warmly welcomed by the mayor, Kiista P. Isaksen and her team: Kenneth H. P. Høegh, Kim Dahl, and Palle Frederiksen. After a brief introduction in Greenlandic and English about the municipality, that by the way is the size of Switzerland, the politicians are very interested in what our cruise leader has to say about the fish stocks. Mr. Werner is at his best, makes a great impression, and gets invited to speak to the local fishermen the next morning. Fishing here really means everything!

We close the day with a fine meal of muskox steak and move on to the legendary Rock Cafe. Here the qaqortesque two-man-rock-group heats up the house and brings us all on the floor. Happy and packed with memories and diesel we leave the harbor the following day. What a trip!”

After refilling the ship with fuel and food, we were hit again by a strong storm, which forced us to seek shelter in one of the Fjords around Qaqortoq. This year is truly a (sad) record year in terms of storms in the survey area. However, Serra Örey, a Master’s student from GEOMAR in Kiel and part of the scientific staff, is willing to share some of her thoughts and emotions from the survey:

“I am Serra, studying my Master’s degree in Biological Oceanography in GEOMAR in Kiel, Germany. As my master thesis is also about cod but from a different stock (Baltic Sea), I am very happy to meet with the huge “Kabeljau” of Greenlandic waters. I feel extremely lucky to be part of an international research cruise to witness how big and connected the ocean is and how important it is to work together to understand it better.

On our journey, we are not only getting hands on experience in fisheries research but also gaining unique memories. To name a few: watching whales during our coffee breaks between the fishery hauls, enjoying polar lights before going to bed or trying to spot polar sea birds between icebergs. It is indeed very cool to be a marine scientist.

But as all the beauty comes with a cost, once again, we had to seek shelter in one of the fjords of south west Greenland. So far during our hide out between the beautiful mountains, we had all sort of weather events. From a very calm day with sun where we were right in the eye of the storm, to snow storms with wind force 12 and wind speeds up to 40 m/s.

It is fascinating to see the sea birds flying against snow and keep feeding against the rapid temperature drops. One cannot stop wondering what is going on in depths of the ocean. To have a peek into that, after many days of storm break, we were finally able to catch more cod on November 4th. We hope to do more. If fish can cope up with such environment and move across borders, so do us.

Despite of all the storm breaks, we were still able to collect a large amount of valuable and unique data. Among these are the samples for Ina Stoltenberg, a Master’s student from GEOMAR in Kiel, who writes her Master’s thesis in cooperation with the Thünen-Institute for Sea Fisheries about Atlantic cod in Greenland waters:

"My name is Ina and I am studying biological oceanography at GEOMAR in Kiel. As it is part of my master’s thesis, I have the privilege to participate in this survey. While everyone else is analysing the daily catches, Serra Örrey, another master student from GEOMAR, and I are taking tissue samples of liver and gonad of female mature Cod, to analyse their total lipid content and lipid composition later in the lab. Combined with many other parameters I want to use these data to evaluate the state of somatic condition of the Atlantic cod around Greenland and if different habitats around the Island with different current systems and depth are influencing the condition of the fish. I am especially interested in the impact on the fecundity of female cod, since they are of high relevance for the reproductive potential of the stock."

Like every other journey, this journey also has to come to an end. After another massive storm had forced us to leave West Greenland, we completed our last hauls in the East, where we were able to collect a large amount of valuable data. This year, the annual German Greenland survey has again substantially contributed to a sustainable exploitation of the marine resources around the largest island on this planet.

Our international research team was able to complete a diverse scientific programme; in addition to the standard sampling protocol, hundreds of finclips were taken for genetic investigations, gonad and liver samples for lipid research and plankton hauls for a community analysis. At the same time, we were able to strengthen old and new cooperations. I am convinced that outstanding research on a global scale is only possible with intensive international collaboration and inter-institutional data exchange.

Cruise leader Karl Michael Werner (© Karl-Michael Werner/Thünen-Institut)

At this point, I want to say goodbye and thank you to everybody who followed our blog on this adventure. I also want to thank the crew of our research vessel Walther Herwig III. The cooperation on board was excellent, the atmosphere friendly and the motivation extraordinarily high. Despite the bad weather conditions, we were able to achieve fantastic results. By the end of the week, we will be happy to be home, and sad to leave.

With best regards
Karl-Michael Werner