Aquaculture for all

Urchin Adventure - Science Advances 'Delicacy' Production

NORWAY - Farming of sea urchins is in the wind - and there are already several Norwegian sea urchin farmers. Over a period of many years, Nofima scientists have acquired knowledge that now makes sea urchin farming possible.

"The sea urchin is new as an aquaculture species," says Senior Scientist Sten Siikavuopio at Nofima (formerly Fiskeriforskning).

"If you are to succeed with farming them, you have to understand the conditions in which they thrive and grow."

Siikavuopio has studied sea urchins for several years with a view to achieving profitable farming of both wild-captured sea urchins and those farmed from larvae.

Senior Scientist Sten Siikavuopio (background) takes samples of sea urchins after the feed trials. Colour charts are used to determine the colour of the roe.

Gentle added value

Sea urchin roe is a delicacy in demand, but the wild sea urchin stocks are heavily over fished and catches are significantly reduced. Farming of sea urchins will provide an opportunity to meet the demand and, at the same time, contribute to protecting the remaining wild stocks.

This is something that both scientists and sea urchin farmers are occupied with.

"A lot of things need to be put in place before you get into sea urchin farming," says Siikavuopio.

"What technology should you choose? What water temperature and water quality should they have, what do they like to eat and how much space do they need? Through our research, we have acquired knowledge about this, but there is still a lot to learn."

Brainless creature created worries

Over a three-year period, he studied sea urchin behaviour in order to find out the optimal farming conditions. During this time, he discovered that the sea urchin's behaviour is extremely unpredictable, something which makes it difficult to farm.

"Sea urchins don't have a heart or a brain," says Siikavuopio. "How it is possible for it to orientate itself and survive remains somewhat of a mystery."

"Every so often it can turn over and use very little energy, but certain stimuli start the processes," says Siikavuopio, explaining that sea urchins gave the scientists a surprise when they first began to individually tag the shellfish.

"We had a group of sea urchins in a tank and we attached tags to the spikes. But when we returned after lunch all the tags lay at the bottom of the tank. We couldn't work it out," says the scientist smiling, before adding an explanation: "We discovered that the sea urchins had simply got rid of the spike with the tag. When irritations arise, they get rid of the spike and a new one grows."

The solution was to inject the tag through the shell so the sea urchins could not get rid of them.

“Strongylocentrotus droebachiensis” – also known as the Drøbak sea urchin or green sea urchin – is about to secure a pellet.

Creating a traffic jam

Sea urchins move using small suction cups. An adult sea urchin operating at top speed can move 10 cm per minute. It looks like where they move is a complete coincidence, but they have a good sense of smell and follow the food.

When the sea urchin finds food, it stops and waits until the food is eaten up, something which may take an entire week. A sea urchin that travels backwards and collides with another sea urchin is stuck until the first sea urchin moves. In the space of a week, the queue can get long.

"After having observed chain collisions, we can conclude that sea urchin farmers shouldn't have too many sea urchins in each tank," says Siikavuopio. "Having too many in one tank can mean lots of collisions and queues and the sea urchins being exposed to serious injuries."

As well as having the correct number of sea urchins in each tank, it is also important to ensure the feed is well dispersed to avoid collisions.

Sea urchins enjoy being on walls. This purpose-built tank with corrugated walls will assist the sea urchins to thrive.

Tanks without flat walls

To ease the traffic problems, the scientists have developed a tank with corrugated walls. Sea urchins prefer to be on walls and other vertical surfaces than on the tank floor. Scientists believe this results from the fact that body waste is excreted through a small hole on top, and that this process is easier if the force of gravity assists.

To successfully farm sea urchins, it is necessary to know about what they like to eat, how much and, just as important, when they like to eat.

"Food intake halves in winter, but the shell grows the same amount year-round despite the large variations in feed intake," says Siikavuopio, adding: "In addition, the feed must contain the correct nutritional content and you need to adapt the pellet's surface and shape for sea urchins."

Nofima has also developed a special feed for sea urchins that has achieved extremely favourable test results and may soon be on the market.

The knowledge that has been acquired will also be beneficial when assessing possible commercial operations in other places, such as Greenland.

Sea urchin roe of the highest quality.

Coming to a shop near you?

Sea urchin roe is most popular in Asia, particularly in Japan, where it is often served as a snack on festive occasions. What does the scientist think about the chances of finding this orange delicacy also on shop shelves here in Norway?

"We know that the sea urchin is extremely healthy. Indigenous peoples in countries like Chile, New Zealand and Canada have always eaten sea urchins because of the large amounts of protein and healthy fat the roe contains. With an increasing focus on healthy food, perhaps we will follow their lead."

Siikavuopio has already started his next sea urchin project. In collaboration with Bodø kråkebolleklekkeri (sea urchin hatchery), he will study shell growth with different feeds. The objective is to gain the fastest possible shell growth and the highest possible survival rate.

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