Krill fishery

The krill fishery is the commercial fishery of krill, small shrimp-like marine animals that live in the oceans world-wide. The present estimate for the biomass of Antarctic krill (Euphausia superba) is 379 million tonnes. The total global harvest of krill from all fisheries amounts to 150–200,000 tonnes annually, mainly Antarctic krill and North Pacific krill (E. pacifica). The krill fishery is the commercial fishery of krill, small shrimp-like marine animals that live in the oceans world-wide. The present estimate for the biomass of Antarctic krill (Euphausia superba) is 379 million tonnes. The total global harvest of krill from all fisheries amounts to 150–200,000 tonnes annually, mainly Antarctic krill and North Pacific krill (E. pacifica). Krill are rich in protein (40% or more of dry weight) and lipids (about 20% in E. superba). Their exoskeleton amounts to some 2% of dry weight of chitin. They also contain traces of a wide array of hydrolytic enzymes such as proteases, carbohydrases, nucleases and phospholipases, which are concentrated in the digestive gland in the cephalothorax of the krill. Most krill is used as aquaculture feed and fish bait; other uses include livestock or pet foods. Only a small percentage is prepared for human consumption. Their enzymes are interesting for medical applications, an expanding sector since the early 1990s. Krill are small animals, considered a type of zooplankton, and hence need to be fished with fine-meshed plankton nets. Such nets pose several problems: they tend to clog fast, and they have high drag, producing a bow wave that deflects the krill to the sides. Trawling must hence be done at low speeds. Additionally, fine nets are delicate, and the first krill nets designed exploded while fishing through the krill schools. Furthermore, fine nets increase unwanted bycatch, such as fish fingerlings, which might have unforeseen side-effects on the ecosystem, even though large krill aggregations tend to be monospecific.