Monday, July 30, 2007

Krill fact sheet

Krill is good food! Whale eat food, krill eat LOTS of Krill! 

Did you ever see a reddish patch in the ocean? If so, know that you may have seen a swarm of krill (food for Baleen whales). Krill are tiny animals are very nutritious and very rich in fat. Krill look like small shrimps that have an average length of 1 to 2 cm (although some species can be up to 15 cm in length). Krill is actually the name given to all small animals belonging to superorder Eucarida, which includes 146 known species. In the Azores we have only one species  - the northern krill Meganyctiphanes norvegica  (M. Sars, 1857)

Morphology
The adults of this species can range from 2.2 cm up to 4.5 cm in length. They have reddish or yellowish colouration which is caused by their diet (phytoplankton such as diatoms). Sometimes the females develop a blueish color during the spawning season. The eyes are round and black and are large in comparison to the body size (normal in small individual you can, clearly, see the dark eye.

Habitat
Horizontal distrubution - This species could be found only in the North Atlantic and subarctic Atlantic, from the western side of Greenland to southward near cape Hatteras. Their eastern range occurs between Iceland, Great Britain and Barent Sea and extends southwards to the Mediterranean and North Africa.
Vertical distribution - This species lives between 100 to 400 m during the day, with the maximum depth recorded at 1500 m (recorded in west of Scotland - in the Rockall). During the night they migrate to the surface (in most regions) especially in coastal habitats. Sometimes during the morning it is possible to observe  dense swarms of krill at the surface.

Life cycle
  • During the Spring the females spawn several clutches of eggs - brood size 350 up to 550 eggs (egg size 0.5 mm).
  • After fertilisation the eggs brood, and the naupilii are born (plural of nauplius). This is the typical larvae of crustaceans (shrimps, crabs, etc).
  • Several stages follow (a total of 12 stages until the juvenile stage).
  • The juveniles resemble adults and molt regularly until they reach the adulthood.
Longevity: 1 - 2 years
Breeding age:
1  year

In other languages
Portuguese:  Krill-do-norte
Spanish: Krill mortenõ 



 
Underwater photos of krill



Sample of krill



Cory's shearwater taking off after feeding on a swarm of krill
Notice the krill leaping out of the water


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