Author:  Conor Graff

North Pacific Krill

By Conor Graff

Common Name: North Pacific Krill

Scientific Name: Euphausia pacifica

Size range: Between 16 and 25mm

Identifying features:

The North Pacific Krill is an ocean-based crustacean that can grow up to 25mm in length (this is a bit of a stretch, however; most average around 16mm). The word Euphausia is Latin for ‘brightly shining’, and indeed, these small invertebrates are noted for what appears to be a bioluminescent characteristic throughout their species. North Pacific Krill have large black eyes and large abdomens, and closer inspection reveals what appear to be gills formed around their legs, and scales on their antennae (these scales are very large and used to protect their antennae from damage).


The North Pacific Krill live, as their name would suggest, on the ocean of the same name. This stretch in habitat runs from the southernmost coasts of the US all the way to Japan, and due to their instincts to band into close ‘clouds’ of themselves, they can cover large areas as a quasi-community without having to move from one place to another. However, the accumulation of these krill is anything but organized; while krill can accumulate into these areas of themselves, they usually form these clusters in areas that would be the most hospitable. The gist is that these krill can be found in very large quantities around the stretch that is their habitat, while other areas are completely barren of krill.

Krill tend to dwell in the ocean’s “twilight zone” (the area between the ‘surface zone’ and the ‘bottom zone’), wherein they can stay out of the reach of most surface zone-dwelling predators. Krill swim to the surface zone during the night, where, under cover of darkness, they can find and feast on their food source, phytoplankton.


As mentioned above, krill feed mostly on phytoplankton (“plant plankton”), making them herbivorous. They feed via a complicated system in their mouthparts wherein the phytoplankton is filtered out of the water into the krill’s jaws.

Krill do not feed exclusively on phytoplankton; many are omnivores who feed of animal plankton (zooplankton). As mentioned before, Krill only come out at night to feed (all the better in escaping from hungry predators).


Krill are perhaps the richest form of protein in the entire ocean, which may be why a certain surface-dwelling species (humans) have discovered and started harvesting them.

They tend to be a primary diet of baleen whales and a number of fish (notably salmon); however, humanity has begun to take an interest in these small creatures. In BC, krill are fished out in large quantities in order to feed aquariums, fish farms, and ourselves; Japan is also immensely interested. Those who have tried krill tend to say it has no taste when fresh and raw; however a bitter, powerful flavor is created from krill that is dried out in the sun or frozen.

Life Cycle:

Krill reproduction starts out in a familiar way to nearly every living creature: that with the release of sperm. Upon receiving the male Krill’s sperm, females store the semen in their bodies and fertilize them, and proceed to release the eggs that come out of this union. A female can release up to 20 000 eggs at a time in clusters with intervals in between.  The eggs are laid several hundred meters in the twilight zone, where the larvae can safely hatch without being attacked by most day-dwelling creatures. Upon hatching, krill larvae feed of the nutrients given by the egg yolk. Larvae soon develop through many stages in order to finally reach their adulthood.


Online references:


  • Pechenk, Jan A., Biology of Invertebrates [Fifth Addition]

Photo by D. Young

Video by Conor Graff

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