Topic: Deep-water shrimp

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    The shrimp in the Barents Sea can reach 16 cm and 20 g. It can live for maximum 10 years.

    Photo: Øystein Paulsen / Institute of Marine Research
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    Pandalus borealis 

    Photo: Erling Svensen / IMR
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    Three different sorts of shrimp.

    Photo: Heidi Kathrine Gabrielsen / IMR
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    Taking samples.

    Photo: Torhild Dahl / IMR

Deep-water shrimp/Northern shrimp (Pandalus borealis) is the most important shellfish resource in the North Atlantic, with a fishery of about 250,000–400,000 tonnes annually. The species is also found in colder parts of the Pacific Ocean. 

The shrimp is most common at depths of 100–700 m, but is found both shallower (up to 20 m) and deeper (900 m) – in temperatures between 1 and 9 °C. 

During the day, the shrimps are at the bottom where they rest or graze on organic sediments, small crustaceans, worms, etc. At night, they move up into the water column to graze on zooplankton. Horizontal migrations are less common, but egg-carrying females tend to move towards shallower water around hatching. Shrimp is the food for many fish species, especially cod, but is also been found in the stomach of seals. 

The shrimp begins life as a male. When it is 2–6 years old, it changes sex and turns into female. Age at sex change increases the further north the shrimp populations are found. Female shrimp spawn in June–October, depending on the temperature. The eggs are carried between the legs on the underside of the female until they  hatch in March–June the following year, again depending on the temperature. An average female spawn about 1,700 eggs. When they hatch, the larvae float to the upper layers of the water column where they graze on small plankton. Shrimp grows by molting: it crawls out of its old shell, and the body begins to take up water and increases in size before the new soft shell hardens. The actual growth then takes place gradually by replacing the absorbed water by tissue. Females, which carry their eggs "glued" to the shell, can grow only when they are not egg-bearing.

Pandalus borealis can be up to 10 years old and reach a length of 15–16 cm.