How to Store and Transport Live Snow Crab

 Production biology  

Trials carried out by Nofima show that snow crab has certain characteristics that make it well suited for live storage and sale. This guide shows how.

Contact person
Portrettbilde av Sten Ivar Siikavuopio
Sten Ivar Siikavuopio

Senior Scientist
Phone: +47 976 98 241
sten.siikavuopio@nofima.no

Introduction

The guide was developed on behalf of the Norwegian Seafood Research Fund (FHF).

Currently, the most common method of storing live snow crab is in fish tanks that are supplied with water from both the bottom and the top of the tank. Nofima trials show that the crabs may be stored for up to two months in such tanks without detriment to quality or animal welfare. In order to prevent the crabs from losing weight during two months of live storage, maintenance feeding is recommended.

Trials have shown that snow crabs have an extreme affinity for the cold and are most comfortable at temperatures under 6 °C in pure seawater.  Scientists also recommend cooling the water during the summer and autumn when the water temperature rises above 5 °C. Oxygen levels should be monitored daily and should not drop below 80 percent saturation. The crabs are sensitive to both low and varying levels of salinity in the water. Therefore, one should use pure seawater.

Crab Welfare

A visual inspection of snow crabs allows one to see whether they are suitable for live storage/shipment, or if their condition is so poor that they should be slaughtered immediately.

“We have chosen to use colour codes  (“traffic light system”) for three different criteria – the crab’s movement, its ability to grip and the lifting of claws. These criteria make it easier to symbolise what should be done. Snow crabs that fall into the red category should not be exported alive or continue to be stored alive”, says Senior Scientist Sten Siikavuopio at Nofima.

The guide also provides good advice for companies that want to export live snow crab. Under right condition snow crab can withstand 48 hours of dry transport in air freight boxes using current packing techniques, similar to red king crab.

“In light of the new results, a unilateral focus on large ocean-going processing or factory vessels will be both naïve and limiting regarding the development of this large, new resource. This is just a broad research project where all value chains are taken into consideration, which can optimise the value of snow crab in the future” says Bjørn Ronald Olsen from Cape Fish Group AS, a partner in research projects involving snow crab.

The guide can be found below, or in a printable format here (PDF). (Norwegian language)

This is how it is done:

I. Live storage of snow crab

Currently, the most common method of storing live snow crab is in fish tanks that are supplied with water
from both the bottom and the top of the tank. However, such tanks are not the best solution in relation to the maintenance feeding of
snow crab.

When storing snow crab, the following should be taken into account:

Temperature
• Our trials show that the snow crab is a cold-loving species that is most comfortable below 5°C.
• Therefore, we recommend cooling the water during the summer and autumn when the water temperature rises above 5 °C.

Water quality
• Ensure a good water supply, preferably from the bottom up, using nozzles that distribute
the water over the entire bottom of the tank.
• Oxygen levels should be measured daily, and wastewater saturation levels should be above 80%.
• Snow crabs are sensitive to low salinity and variations in salinity. Therefore, the crabs should be kept in pure
seawater (30–34 ‰).

Density of individuals
• We recommend that the density of individuals for live storage in tanks should be 25–50 kg/m3.
• The number of injuries and the mortality rate increases when the density of individuals is above 50 kg/m3.

Live storage and duration
• Our trials show that the snow crab is a robust animal that can withstand periods without food of
up to 2 months. This is assuming that the crabs are stored at their optimal temperature (< 5°C).
• In order to prevent the crabs from losing weight during two months of live storage, maintenance feeding
is recommended.

II. Assessment of crab welfare

A visual inspection of snow crabs allows one to see whether the crabs are suitable
for live storage/shipment, or if their condition is so poor that
they should be slaughtered immediately.

We have chosen to use colour codes for three different criteria (the crab’s movement, its ability to grip and the lifting of claws). These criteria make it easier to symbolise what should be done, given various welfare scores.

Snow crabs that fall into the red category (welfare score 0) should not be exported alive or continue to be stored alive.

 

Table Welfare score for snow crab

 

III. Transportation of live snow crab

  • Snow crab can withstand 48 hours of dry transport in air freight boxes using
    current packing techniques (similar to red king crab).
  • During the transportation of live snow crab, waste materials accumulate in the blood.
    The majority of these waste materials will be excreted via the gills when the crab
    is returned to water. Therefore, the crabs require fresh seawater immediately after transportation in order to
    purge themselves of accumulated waste materials.
  • Temperature is the most important single factor affecting the amount of
    waste materials. Refrigeration before transport lowers the crab’s metabolism and production of waste materials. To achieve the best effect, the crabs should be cooled to
    below 1ºC.

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