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King crabs shows promise for aquaculture

Fish stocks Crabs Nutrition +5 more

Researchers in Norway believe that king crab farming has significant commercial potential, following a year of trials.

Grete Lorentzen with a on-grown king crab

The crabs are growing well and have made it through their first, critical moult © Lars Åke Andersen, Nofima

During the past 12 months researchers at Nofima say they have now developed “the right food, the right environment and the right conditions” for ongrowing wild-caught king crabs – a non-native invasive species in Norway.

“The crab has turned out to be a good candidate for rearing, and has now become a farm animal, which we have gradually learned how to manage. We know much more about what it takes for crabs to thrive in captivity: to eat, grow and be nice to each other. And we are now in the process of determining the right feed as well,” said Sten Siikavuopio, a long-time crab researcher at Nofima, in a press release.

“If we succeed, we will potentially have laid the foundation for a completely new industry in western Finnmark,” added Grete Lorentzen, who is also an experienced crab researcher and head of the “Helt Konge” (crab is king) research project.

From unwanted invader to tasty treat

In the 1960s, red king crab – Paralithodes camtschaticus – was released into the Murmansk fjord. Since then, they have spread along the coast of Finnmark until Troms county.

East of Honningsvåg the red king crab fisheries are highly lucrative, and regulated by quotas. However, west of the North Cape, they are considered an invasive species. Norwegian fisheries authorities intend to reduce the crabs’ presence west of the quota-regulated area and have therefore established a free fishing zone west of Honningsvåg. In this zone, the crabs can be captured and brought onshore regardless of size.

The problem is that this is not an attractive fishery for professional fishermen – the crabs caught west of Honningsvåg are generally too small for buyers in the international market, who want Norwegian king crabs weighing at least 1 to 2 kilograms.

Vulnerable during moulting

A year ago, researchers started feeding small crabs, weighing about 250 grams, obtained from the free-fishing area. This is a part of the research study, and the aim is to reach a weight of 1.6 kilograms or more after three years of the project.

“Before we get that far, the crabs have to undergo multiple changes of the shell – moulting, that’s how they grow. The moulting stage is a critical phase for the crab, as that’s the time when they are the most vulnerable,” explained Siikavuopio.

The crabs in the Nofima project have to go through 3-4 such critical moults to reach commercial sizes. After achieving an initial successful moult, the researchers are optimistic.

“So far, the results have exceeded all expectations. The moulting indicates the crab grows well, and the mortality rate associated with the moulting was less than ten per cent, which are excellent numbers,” explained Siikavuopio.

The extent of the in increases in size and weight per moult is an indication of how well the crab is doing.

Knowledge about live storage and feeding of small king crabs will be in high demand

The Nofima scientists believe that knowledge on how live storage and feeding of small king crabs should be done, will be in high demand both in Norway and abroad. Developing such knowledge is also in line with Nofima’s goal of being a leading business-oriented research institute that conducts research and development for the aquaculture, fisheries and food industries.

“Nofima’s strength lies in its interdisciplinarity. We have biologists who understand what it takes to make the animals thrive, and our colleagues at the research station in Bergen produce the feed we use, based on our knowledge of what works best for crabs. In addition, we have expertise in product quality and consumer perceptions, which allows us to have an approach where we consider the entire value chain in our work”, says Siikavuopio.

As with all animal farming, time and feed costs are critical factors in terms of profitability. By starting with wild-caught small crabs, it is possible to save both time and feed costs.

“And if we start with slightly larger crabs than we used in the study, less feed will be required before the crab reaches a size that’s attractive to the market, thereby avoiding large feed expenses,” stated Grete Lorentzen.

Food fit for kings from residual raw materials

The great thing about the king crab is that it will eat practically anything, making it a great candidate for farming. Running in parallel with the “Helt Konge” project is the research project “Kongemat” (Food for kings), where scientists are busy investigating how residual biomass from other marine species - such as lumpfish and shrimp shells - can be used as a feed source for farmed crabs.

“You see, the crab eats like a four-year-old – half the meal ends up on the floor. We are therefore working to develop a feed with a structure that minimises spillage,” explained Siikavuopio.

The traditional approach in aquaculture has been to feed animals on a daily basis, but the Nofima scientists believe they might benefit from reconsidering this approach.

“For example, three times a week instead of every day. In theory, that would make it ingest everything it spills to the floor during the first ‘serving’,” added the researcher.

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