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Erik Furevik collecting water samples. Photo: Ingrid Wollberg

Research using earmuffs and fishing rods

almost 3 years ago
Written by Ronald Toppe
Ocean research > Research using earmuffs and fishing rods

Research using earmuffs and fishing rods

almost 3 years agoOcean research
Written by Ronald Toppe
Erik Furevik collecting water samples. Photo: Ingrid Wollberg

Sailing from Norway to Spain and Portugal in great summer weather has been an adventure. But the voyage is first and foremost an expedition to gather new data, gain new insights, and then share the new knowledge.

All that can be measured, will be measured, from the weather and waves, to the conditions down in the sea.

Data collection is handled by students Erlend Mundal and Erik Furevik. They monitor the instruments that takes water samples, analyze and report, they look for whales and dolphins, and they fish. You read that right, fishing with a fishing rod.

Erik Furevik and Erlend Mundal. Photo: Ingrid Wollberg
Erik Furevik and Erlend Mundal. Photo: Ingrid Wollberg

Every morning, in the middle of the day and in the evening, the rods are put to use. One rod is for fish of normal size, the other so strong that it can catch fish weighing more than 20 kilos.

It was Geir Huse at the Institute of Marine Research who got the idea to equip the students with fishing rods.

Research director Geir Huse at the Institutet of marine research. Photo: Ronald Toppe
Research director Geir Huse at the Institutet of marine research. Photo: Ronald Toppe

- I don't think this has been done before, at least I do not know about it, he says.

Doing ocean reseach, it is common to use how much fish you manage to catch as a measure of how much fish there are in the sea in total. The researchers call it "catch per unit effort". The unique thing here is that normal fishing rods are used, systematically around the globe - 55,000 nautical miles, 102,000 kilometers.

- What we manage to catch is exciting, but also to have a time series. How often do we get a fish on the hook, along the entire route, says Huse.

Fishing in the sunset Photo: Jesper Rosenmai
Fishing in the sunset Photo: Jesper Rosenmai

The catch is photographed, weighed and measured, and the ear stones are picked out. The ear stones are part of the balance organ of the fish. If you split them in two, you will see annual rings that tell how old the fish is, just like in trees.

- The size of the fish provides some information, but the age of the fish is much more important to us, says Huse.

The catch does not go to the seagulls, but to the chef. On a ship, there is a limit to what you can bring in provisions, and fresh fish is delicious. No fish - so far.

- Of course, two small rods in a large sea, it is not a given that you get fish, says Huse.

Marine research vessel

Counting the number of fish caugth is not sufficient. The researchers will also find out if there is a connection between how often fish bites the hook, and other conditions in the sea. So, before the cruise began, Statsraad Lehmkuhl was equipped as a modern research vessel.

One of the instruments takes water samples, completely automatically. The system is called "Ferrybox".

Erik Furevik checks the Ferrybox in the engine room. Photo: Ingrid Wollberg
Erik Furevik checks the Ferrybox in the engine room. Photo: Ingrid Wollberg

- It takes samples of CO2 and oxygen content, chlorophyll - that is the amount of phytoplankton, temperature, and salinity, about once a minute. Ferrybox is a well-established system, installed on many ships, the ferries that cross the North Sea for example. It gives very good data, but the limitation is that the samples are taken from the water intake at the bottom of the ship, only about eight meters down, Huse explains.

They will therefore stop Statsraad Lehmkuhl at regular intervals. The ship has a sampler that can be lowered all the way down to 750 meters. A valve is closed, and then the water sample is pulled back on board.

Once the ship is at rest, a plankton net is also sent 200 meters down. The net has a very fine-meshed cloth, which collects plankton when it is slowly hauled up.
Plankton are tiny animals and plants that float around in the ocean. In a liter of seawater there can be tens of millions of them, and they are important food for fish and other animals.

- The plankton samples give us a lot of information, but they must be analyzed by experts on land so the contents of the net are preserved in alcohol, Huse says.

Checks for genetic material

The water samples will be checked for microplastics; tiny pieces of plastic bags, plastic bottles, remnants of ropes and other things, torn and broken by the waves. We also release microplastics when we wash synthetic clothes. The warm fleece jacket that is so nice and cosy has a problematic side to it.

Water sample. Photo: Ingrid Wollberg
Water sample. Photo: Ingrid Wollberg

DNA, genetic material, is also extracted from the water samples. The technique is called eDNA, which stands for environmental DNA.

- I am very excited about this, says Huse.

The technique has been known for a long time, but has been in practical use only the last five years. Everything that lives in the ocean releases some DNA, and there are now large databases that the samples are checked against. A list of organisms present in the area where the sample was taken is issued automatically.

- Even if you do not get the organism up, this is a completely certain identification, says Huse.

Many organisms stay down in the depths during the day, and only come to the surface during the night. Since the water samples are taken around the clock, Huse and his colleagues can study how this "commuting" takes place, and see if there are differences around the globe.

- To get DNA out of the water samples, we use special filters. Some of them are frozen and stored, while others are analyzed on board. So they get a species-list there and then, and that's a bit exciting. This is one of the more complicated tasks the students do, and which they needed a full day of training to perform, says Huse.


Statsraad Lehmkuhl has a new echo sounder installed. Not for safe navigation, but to discover what lives down below the ship.

On the echo sounders installed in our day cruisers, many strange things show up as fish symbols. This is not the case here, the echo sounder on board know the difference between plankton and fish.

- You can not visually see very far down into the sea, but the echo sounders reach all the way to the bottom, and give us an incredible amount of information, says Huse, and explains.

- We can look at how much plankton there is in the Atlantic in relation to in the Pacific Ocean and the Indian Ocean for example. And we can see if there is a connection between what we register of phytoplankton measured by Ferrybox in the upper layers, and the amount of fish further down, for example. How deep down do we find the zooplankton? Is there a connection between the organisms and the amount of sunlight?


If you put on a diving mask and dips your head into the ocean, it may seem empty and silent. But that's not the case. The animals that live down there make noise, and so do ships. The sound propagates more than four times faster in water than in air, and layers of water with different temperatures and salinity, creates "channels" that allow the song of a whale to be heard many kilometers away.

Huse will also investigate this, and has installed hydrophones on board - microphones made to function underwater.

- It will be very exciting to find out what we hear. What is man-made noise, and what is biological sound? And how the sound is distributed. We will look for relationships between natural sounds, noise, and other parameters, says Huse.

Doing research from a sailing ship has several advantages. Photo: Ingrid Wollberg
Doing research from a sailing ship has several advantages. Photo: Ingrid Wollberg

When you want to record sound using hydrophones, it is perfect to be in a sailing ship, which does not make noise itself.

- We can tow a hydrophone behind a boat with an engine as well, but now we remove noise from the ship almost completely. It's the same with echosounders. The fish are scared away by a boat that moves using a large propeller, Huse explains.

Erlend Mundal on whale watch. Photo: Ingrid Wollberg
Erlend Mundal on whale watch. Photo: Ingrid Wollberg

Watch for whales

Erlend and Erik will also watch for whales.

At regular intervals, they will scout the sea with binoculars. When they see a tail fin, or a blow - the cloud of water and steam when the whales breathe, they note the position and time, and what species they have seen.

The latter is a challenge. Marine scientists usually bring in special experts for counting whales, people who can recognize the different species based on the way they behave.

- The students do not have that experience, but they can at least see that here is a whale, and then they can eventually wind up what species it probably is. But just knowing that there are whales, and their numbers, helps us to understand the productivity, the amount of phytoplankton and fish, Huse says.

A dolphin swims close to the ship, a common sight along the coast of Portugal. Photo: Ingrid Wollberg
A dolphin swims close to the ship, a common sight along the coast of Portugal. Photo: Ingrid Wollberg

Guinea pigs

So a lot of responsibility rests on the shoulders of the students, and Huse is honest - as the first two are Erlend and Erik are guinea pigs.

- They are in a way double test guinea pigs. They will have to get the systems to run smoothly, we have not run the systems, we have tested them, but have not run them over time. And beeing the first, find out how much one can expect to get done in the course of a day. Now, this it is a bit unclear simply.

Agenda Vestlandet, a foundation established by Sparebanken Vest, makes it possible for Huse to have students on board during the entire cruise. They have paid for the equipment that is installed, and cover the costs of the total of 20 students who will share the work.

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The One Ocean Expedition is a circumnavigation by the Norwegian tall ship Statsraad Lehmkuhl. We aim to to share knowledge about the crucial role of the ocean for a sustainable development in a global perspective.

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