Fishing to find out

This article was published during the One Ocean Expedition 2021-2023.

One Ocean Expedition is a research expedition and everything that can be measured must be measured. From weather, wind and waves, to the conditions in the ocean. How salty the seawater is, how much oxygen it contains, and whether it is contaminated by microplastics. And what lives down there, from tiny plankton to huge whales.

Several methods

Several methods are used to find out what kind of organisms that live around the ship.

The students responsible for the research equipment on board extract DNA, i.e. genetic material, from seawater that is pumped into the laboratory down in the ship. All species have a completely unique "fingerprint", and a small piece of organic material is all it takes to identify a species.

The seawater is filtered, and what accumulates in the filter is processed. Some analyzes are done on board, others are done in advanced laboratories on land, on material that is frozen and sent home.

An advanced sonar sends sound waves into the sea, revealing how much fish and plankton live down there, and how the organisms move between the surface and the depths throughout the day.

Stops up

Statsraad Lehmkuhl is stopped at regular intervals, so that the students can lower instruments into the ocean and take samples. With a plankton net they pick up some of the tiny animals and plants floating in the seawater.

A hydrophone; a microphone that works underwater, is towed behind the ship and listens for the sounds the whales make. Each species has its own melody.

The hydrophone cannot be used all the time, and the students also have look-out watches, where they use binoculars to look for whales, and make records of the species they spot.

Fishing rods

Two fishing rods are mounted on the railing of Statsraad Lehmkuhl. They are often used by the crew, fishing is fun, fresh fish is good food, and a popular, short-distance and sustainable addition to the food stock. But the fishing rods are also part of the research equipment.

Three times a day, the students hook a lure on the line and let it go. One fishing rod is for fish of normal size, the other is so strong that it can catch really heavy ones.

55,000 nautical miles

If a fish is caught, it is photographed, weighed and measured. If there is no catch, this is also an important research result.

It is common to use how much fish you manage to catch as a measure of how much fish there are in total. The researchers call it "catch per unit effort". What is special this time is that no trawl or net is used, but a fishing rod, and that fishing is carried out systematically throughout the entire expedition, 55,000 nautical miles; 102,000 kilometers.

Before the fish is taken to the chef, the ear stones are picked out. They are part of the balance organ of the fish, and grow all the time. If you split an earstone in two, you see annual rings that tell how old the fish is and how fast it has grown, a bit like sliced wood.

Delicious meals

On the voyage across the Indian Ocean, several fish were caught. The fish in the picture at the very top is not a swordfish, but a sailfish. Sailfish also has an elongated upper jaw, but has a large sail-shaped fin along almost its entire back.

The sail is folded when the fish swims. It unfolds if the fish feels threatened, an attempt to make the sailfish appear large and dangerous.

In the picture above, boatman Torben is holding a golden mackerel, which is also called a dorado.

In Hawaii golden mackerel is called mahi mahi, which means very strong. Golden mackerel has been turned into delicious meals several times during the expedition. The fish can weigh up to 15 kilos, food for a lot of people!

Carpenter Joachim and student Martin are smiling happily in the photo above because they have got a bonito, also called skipjack tuna, on board. This is a fish related to mackerel and tuna, and when you buy canned tuna there is often bonito in the box. Around 2,500,000 tonnes of this species are caught annually, and is really good food.

In the picture below, student Erik and coxswain Kjell-Ove have taken on board a wahoo, which is also related to mackerel. The species is really fast, and can swim at over 40 knots. The wahoo is also very good to eat, but there is no commercial fishing for the species.

A lot of work

All the information that is collected during the voyage, from the physical condition of the seawater the ship is sailing in, to knowledge about pollution and which organisms are present, is a small piece in the puzzle that the researchers are putting together to find out what the state of the ocean is like.

Statsraad Lehmkuhl has been sailing for 14 months now, and has sent home huge amounts of information. Measurement data is continuously transmitted via satellite, while the samples are sent home in packages. Some of it has been analyzed, and the first articles have been sent to research journals for publication.

But most remain, and the ship will be back in Norway long before everything has been analyzed and published.