Krill are tiny shrimp-like marine invertebrate animals that are very near the bottom of the marine food chain.
They are the primary source of food for many species of marine mammals as well as for Manta rays and whale sharks.
The krill fishing ban has been praised by both government marine experts as well as environmental groups.
"This is a great success for protecting the entire California Current ecosystem," said William Douros, West Coast Regional Director for NOAA's Office of National Marine Sanctuaries.
Commercial fishing of krill is done in the Southern Ocean off Antarctica and in the waters around Japan.
Most of the krill caught is used for aquaculture and aquarium feeds, as bait in sport fishing and by the pharmaceutical industry.
Krill is also used for human consumption In Japan and Russia, where it is known as okiami.