3.1 Species with documented commercial potential
Large-scale commercial fishing of krill is a relatively recent phenomenon although there are records of some species of krill being harvested from the nineteenth century (Fisher et al. 1953; Mauchline and Fisher 1969). Their small size and generally sub-surface habit have ensured that krill, of any species, have only been harvested when more desirable or obvious species in an area have been depleted or when they are more readily harvestable, such as when they are in surface swarms.
Antarctic krill: Euphausia superba is one of the bigger species, growing to a maximum size of 6.5cm and weighing up to 2g. Antarctic krill grow to their maximum size over a period of approximately 3-5 years. The fishery concentrates on the larger adults in the 40-65mm size range. Antarctic krill occurs throughout most of the waters south of the Antarctic Convergence but is most abundant closer to the Antarctic continent and around some of the Antarctic and subantarctic islands (Fig. 2). It has been commercially harvested all around the Antarctic although the current fishery concentrates in the South Atlantic with summer fisheries along the Antarctic Peninsula and winter fisheries around South Georgia Island (Miller 1991).
North Pacific krill: Euphausia pacifica is a widely distributed species being found from the Pacific coast of Japan to southern California (Fig. 3). E. pacifica is commercially harvested off the coast of Japan (Odate 1979; Odate 1991) and off the coast of British Columbia, Canada (Haig-Brown 1994).
Euphausia nana is closely related to E. pacifica and is only found in the waters off southern Japan and in the East China Sea. E. nana reaches a total length of 12mm and is harvested commercially off the Japanese coast (Fig. 4) (Hirota and Kohno 1992).
Thysanoessa inermis is found in the North Pacific and in the North Atlantic, particularly in the colder waters but does not breed north of 65-70°N (Fig. 3). It reaches a length of 30mm. It is harvested in both the Japanese coastal zone (Kotori 1994) and in the Gulf of St. Lawrence, Canada (Runge and Joly 1995).
Thysanoessa raschii is found in the North Pacific and in the North Atlantic, particularly in the colder waters and in Arctic regions (Fig. 3). It is commercially harvested on an experimental basis in the Gulf of St. Lawrence, Canada (Runge and Joly 1995). It reaches a length of 25mm.
Meganyctiphanes norvegica is found over a large climatic range, from the subarctic in the waters surrounding Greenland, Iceland and Norway to the warmer waters of Cape Hatteras in the West and the Mediterranean in the East (Fig. 3) (Mauchline 1967). M. norvegica is commercially harvested in the Gulf of St. Lawrence and there is a proposed fishery for this species on the Scotian Shelf, Eastern Canada (Fig. 5) (Runge and Joly 1995). Small scale harvesting of M. norvegica has also occurred in the Mediterranean (Fisher et al. 1953). M. norvegica is a medium sized krill reaching a total length of over 40mm.
Nyctiphanes australis has also been proposed as a species with commercial potential (Virtue et al. 1995). This species is found off South East Australia and from the waters surrounding New Zealand (Fig. 2). N. australis is a small species reaching a length of only 20mm. It is an egg-brooding species of krill.