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- A re-appraisal of the total biomass and annual production of Antarctic krill,
- Despite much research on Euphausia superba, estimates of their total biomass and production are still very uncertain. Recently, circumpolar krill databases, combined with growth models and revisions in acoustics have made it possible to refine previous estimates. Net-based databases of density and length frequency (KRILLBASE) yield a summer distributional range of ∼19×10 6km 2 and a mean total abundance of 8×10 14 post-larvae with biomass of 379 million tonnes (Mt). These values are based on a standardised net sampling method but they average over the period 1926-2004, during which krill abundance has fluctuated. To estimate krill biomass at the end of last century we combined the KRILLBASE map of relative krill density around Antarctica with an acoustics-derived biomass estimate of 37.3Mt derived for the Scotia Sea area in 2000 by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). Thus the CCAMLR 2000 survey area contains 28% of the total stock, with total biomass of ∼133Mt in January-February 2000. Gross postlarval production is estimated conservatively at 342-536Mtyr -1, based on three independent methods. These are high values, within the upper range of recent estimates, but consistent with the concept of high energy throughput for a species of this size. The similarity between the three production estimates reflects a broad agreement between the three growth models used, plus the fact that, for a given population size, production is relatively insensitive to the size distribution of krill at the start of the growth season. These production values lie within the envelope of what can be supported from the Southern Ocean primary production system and what is required to support an estimated predator consumption of 128-470Mtyr -1. Given the range of recent acoustics estimates, plus the need for precautionary management of the developing krill fishery, our net-based data provide an alternative estimate of total krill biomass. © 2008 Elsevier Ltd., Cited By (since 1996):34, CODEN: DRORE, , , Antarctica, Invertebrates
- Atkinson, Siegel, Pakhomov, Jessopp, Loeb
- Oceanic circumpolar habitats of Antarctic krill,
- Surveys of Euphausia superba often target localised shelves and ice edges where their growth rates and predation losses are atypically high. Emphasis on these areas has led to the current view that krill require high food concentrations, with a distribution often linked to shelves. For a wider, circumpolar perspective, we compiled all available net-based density data on postlarvae from 8137 mainly summer stations from 1926 to 2004. Unlike Antarctic zooplankton, the distribution of E. superba is highly uneven, with 70 % of the total stock concentrated between longitudes 0° and 90° W. Within this Atlantic sector, krill are abundant over both continental shelf and ocean. At the Antarctic Peninsula they are found mainly over the inner shelf, whereas in the Indian-Pacific sectors krill prevail in the ocean within 200 to 300 km of the shelf break. Overall, 87% of the total stock lives over deep oceanic water (>2000 m), and krill occupy regions with moderate food concentrations (0.5 to 1.0 mg chl am -3). Advection models suggest some northwards loss from these regions and into the low chlorophyll belts of the Antarctic Circumpolar Current (ACC). We found possible evidence for a compensating southwards migration, with an increasing proportion of krill found south of the ACC as the season progresses. The retention of krill in moderately productive oceanic habitats is a key factor in their high total production. While growth rates are lower than over shelves, the ocean provides a refuge from shelf-based predators. The unusual circumpolar distribution of krill thus reflects a balance between advection, migration, top-down and bottom-up processes. © Inter-Research 2008., Cited By (since 1996):76, CODEN: MESED, , , Downloaded from: www.int-res.com/articles/feature/m362p001.pdf (13 June 2014).
- Atkinson, Siegel, Pakhomov, Rothery, Loeb, Ross, Quetin, Schmidt, Fretwell, Murphy, Tarling, Fleming