|Scientific Name:||Euphausia superba Dana, 1850|
Euphausia antarctica Sars, 1883
Euphausia murrayi Sars, 1883
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Kawaguchi, S. & Nicol, S.|
Antarctic Krill is widespread in the Southern Ocean. Its population size fluctuates considerably, but overall the population seems to be stable. Krill fishery is regulated by the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR) since the 1980s. Krill catches have strongly declined at the beginning of the 1990s and are slightly increasing since this time. The major threat to this species is climate change. Antarctic Krill is considered as Least Concern (LC) because of its large population size and geographic range.
|Range Description:||Antarctic krill (Euphausia superba) live exclusively in the Southern Ocean and have a very wide distribution over a range of habitats. The species has a circumpolar distribution with the largest populations being found in the South Atlantic in the vicinity of the Antarctic Peninsula and island groups. They are a swarming species and much of the krill biomass is to be found in large, dense aggregations that can extend for tens of kilometres.|
Native:Antarctica; Argentina (Tierra del Fuego); Bouvet Island; South Georgia and the South Sandwich Islands (South Georgia, South Sandwich Is.)
|FAO Marine Fishing Areas:|
Atlantic – southwest; Atlantic – Antarctic; Indian Ocean – Antarctic; Pacific – Antarctic
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Krill distribution varies markedly around the Antarctic continent but there is no direct evidence to date of genetic subpopulations. Total population size is of the order of 200 million tonnes. |
The overall mean abundance of krill estimated from scientific net surveys conducted between 1926-2004 was 379 million tonnes (Atkinson et al. 2009). Atkinson et al. (2009) estimated the krill biomass for January-February 2000 to be 133 million tonnes. This estimate was based on an acoustic estimate of biomass derived from the CCAMLR2000 survey of the South Atlantic of 37.3 million tonnes which was estimated to be 28% of the global krill biomass. CCAMLR has subsequently revised this biomass estimate (SC-CCAMLR 2010 para. 3.29) to 60.3 million tonnes. Applying the process used in Atkinson et al. (2009) to this new estimate of biomass results in a global krill biomass of 215 million tonnes in the year 2000.
Although a decline in krill density in the 1970s and 1980s has been reported from analysis of net survey data in the Southwest Atlantic sector (Atkinson et al. 2004) the magnitude of any such decline is difficult to ascertain. For the purposes of this current assessment the trend in krill biomass over the last 15 years (three generation times) has been used. Two time series of acoustic data (the standard method of biomass assessment used by CCAMLR) exist within the range of Antarctic krill – one for South Georgia (Fielding et al. 2014) and one for the Elephant Island area (Cossio et al. 2011). Both of these time series are from the South Atlantic region where 28% of the krill biomass is thought to reside (Atkinson et al. 2009). There is considerable inter-annual (and intra-annual) fluctuation in krill density (either measured acoustically or using nets) at a fixed location, however, in neither of these two acoustic time series is there a significant trend in the data.
|Current Population Trend:||Stable|
|Habitat and Ecology:|
Habitat includes open ocean areas as well as more coastal locations. Highest densities are within 200 km of the continental shelf break. In much of its range it is absent from the coastal zone and deeper embayments where Euphausia crystallarophias is the dominant krill species. Spawning occurs in summer in deeper waters and the eggs sink before developing into a swimming stage which ascends to the surface to feed (Marr 1962). Larvae develop into juvenile over their first year and become mature adults in their second year.
|Continuing decline in area, extent and/or quality of habitat:||Unknown|
|Generation Length (years):||5|
|Movement patterns:||Not a Migrant|
|Use and Trade:||Commercial fishery operating since the 1970s, currently catching 300,000 tonnes annually. Products include krill meal and krill oil for human consumption. The krill fishery has been operating for more than over 40 years. Catches peaked in the early 1980s with Japanese and Soviet vessels catching over half a million tons a year. Today, about 300,000 tons are caught from the South West Atlantic, largely by Norwegian vessels, producing high-end aquaculture feed and krill oil supplements for human consumption (Foster et al. 2011). When the krill fishery was established there was concern that it might cause irreversible damage to the Antarctic ecosystem, so a unique international treaty was signed to ensure it would be managed using an approach that took into account the needs of the entire ecosystem. This treaty was the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR). The management of the krill fishery has been guided by its principles since the early 1980s. The fishery is regulated through a series of measures that specify how much can be caught, where it can be caught, acceptable levels of by-catch and other operational restrictions. The amount of krill that can be caught in any one year is set through “Precautionary Catch Limits (PCL),” which is more conservative than normal fishery quotas because of the sensitivity of the Antarctic krill biomass, the animals that depend on it as a food source, and the unique environment in which they live (Nicol and Foster 2003). Catch limits are calculated for a particular area by working out how much krill is in that area and by determining the proportion of the krill stock in that area that can be harvested without irreversibly impacting the ecosystem in the long-term. Currently, only 9.3% of the krill stock is available to the fishery. Precautionary Catch Limits have been set for several large areas of the Southern Ocean, totalling more than 8 million tons per year. In the South Atlantic, where the krill fishery currently operates, there is a Precautionary Catch Limit of 5.6 million tons. As an added element of precaution, CCAMLR has applied a “Trigger Level” of 620,000 tons throughout the main fishing grounds– a level of catch that cannot be exceeded until more advanced management procedures are in place.|
The life history and population dynamics of Antarctic krill are likely to be impacted by climate change (Flores et al. 2012), and may result in a reduced habitat range (Hill et al. 2013). The reproductive output and recruitment success of krill has been related to the extent, timing and duration of winter sea ice cover. The underside structure of sea ice provides a nursery ground for overwintering krill larvae and a substrate for algae which are their food. Extensive winter sea ice promotes strong spring phytoplankton bloom when retreating in spring which fuels the adults’ reproductive output for their summer spawning season (Quetin and Ross 2001). Krill growth has also been observed to decrease above a temperature optimum of 0.5 degrees Celsius (Atkinson et al. 2006). Their early developmental stage of krill is vulnerable to increased levels of CO2 projected within their habitat range in year 2100 and beyond (Kawaguchi et al. 2013). Overall, the cumulative impact of climate change is most likely to be negative.
|Conservation Actions:||Conservation needs include continued precautionary management of the fishery. This is regulated by the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR). More research on the impact of climate change on this species is needed.|
|Citation:||Kawaguchi, S. & Nicol, S. 2015. Euphausia superba. The IUCN Red List of Threatened Species 2015: e.T64239743A64239951.Downloaded on 20 June 2018.|
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