Krill, that reddish transparent shrimp-like organism; we often speak of, but in reality what is it? In fact, krill is a general term used to describe many species of planktonic crustacean, which includes 85 species of Euphausiids. As an adult euphausiids measure from 1-14 cm (0.5-5.5 inches) depending on the species and with an average weight of 1 gram. They can congregate in massive, dense surface swarms, covering several kilometers, which color the sea surface red. Krill is a vital component of the oceanic food chain, because many species including, seals, whales, marine birds, and myriad fish depend on it directly or indirectly. It is certainly one of most prolific and abundant species on the planet. For example, the female of the largest Antarctic euphausiid (Euphausia superba) produces more than 10,000 eggs at a time, several times per season.
Krill feeds on phytoplancton, simple plant-like organisms that float at the oceans surface. Though krill can be seen at the surface during daylight in certain oceanic regions, it generally stays in deeper water during the day and is more commonly observed at the surface after sunset and during the night. Surface sightings of krill in full daylight do occur, however such occurrences remain unexplained.