Setting a precautionary catch limit for Antarctic krill

A revised precautionary catch limit for Antarctic krill (Euphausia superba) in the Scotia Sea of 4 million tons was recently adopted by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). The limit was based on a total biomass of 44.3 million tons, as estimated from an acoustic and net survey of krill across the Scotia Sea sector of the Southern Ocean, and a harvest rate of 9.1%, as determined from an analysis of the risks of exceeding defined conservation criteria. We caution, however, that before the fishery can expand to the 4-inillion-ton level it will be necessary to establish mechanisms to avoid concentration of fishing effort, particularly in proximity to colonies of land-breeding krill predators, and to consider the effects of krill immigrating into the region from multiple sources

The CCAMLR 2000 Survey: a multinational, multi-ship biological oceanography survey of the Atlantic sector of the Southern Ocean.(Editorial)

The CCAMLR 2000 Survey is the first large-scale multinational, multi-ship survey in the Southern Ocean since 1979/80. Conducted using strict method protocols and within a 32-day time frame it provides a truly synoptic view of the oceanography, zooplankton, krill, and higher predator biomass and distribution for the Scotia Sea and Antarctic Peninsula region. The innovative design of interleaved transects surveyed only during the hours of daylight has provided a comprehensive and robust estimate of krill biomass

Biomass and energy transfer to baleen whales in the South Atlantic sector of the Southern Ocean

Baleen whales are an important group of predators on Antarctic krill in the Southern Ocean. During the CCAMLR 2000 Survey to estimate the biomass and distribution of Antarctic krill, International Whaling Commission observers carried out a visual line transect survey to estimate the number of baleen whales occurring in the survey area. This paper reviews techniques used to estimate krill consumption by baleen whales and in combination with estimates of whale abundance estimates of krill consumption are generated for the South Atlantic sector of the Southern Ocean. This survey estimates that the present populations of whales feeding in this region are likely to consume approximately 1.6 million tonnes, but possibly up to as much as 2.7 million tonnes of krill within the summer season. Although this only represents 4&ndash;6% of the estimated krill biomass in the region (and probably less than this percentage of the total annual krill production), the depleted numbers of baleen whales resulting from past or current whaling activities should be taken into account when setting quotas for the commercial exploitation of krill if there is to be a recovery to pre-exploitation biomass levels of baleen whales.<br /

Factors influencing the distribution, biomass, and productivity of phytoplankton in the Scotia Sea and adjoining waters

During January and February 2000 four research vessels, from Russia, the UK, Japan, and the United States, conducted an oceanographic survey with 137 hydrographic stations within the Scotia Sea and adjoining waters as part of a survey sponsored by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) to estimate the biomass and distribution of Antarctic krill in the Scotia Sea. Chlorophyll-a (Chl-a) measurements showed great variability in phytoplankton biomass within the Scotia Sea, with some areas having among the lowest Chl-a concentrations found in Antarctic waters ( 10 mg m(-3). This paper describes the distribution and concentration of Chl-a in the upper 100 m of the water column and relates the Chl-a profiles at individual stations to profiles of upper water-column stability, to the depth of the upper mixed layer, and to the mixing of different water masses. The 58 stations with the lowest Chl-a values in surface waters also had low values for integrated Chl-a (33.9 +/- 19.5 mg m(-2)) and a Chl-a maximum at depths of between 70 and 90 m, in contrast to all other stations where deep Chl-a maxima did not occur. The T/S diagrams at many of these stations were indicative of Antarctic Circumpolar Current (ACC) waters. The central Scotia Sea and areas to the west and north of South Georgia had significantly higher integrated Chl-a values (98.1+/-46.0 mg m(-2), n = 57), in addition to five stations with very high Chl-a values (mean of 359+/-270 mg m(-2)). The mean rate of integrated primary production, which was estimated using the Chl-a data and the mean incident solar radiation measured from previous cruises as well as from satellite data, was estimated to be 994 mg carbon m(-2) day(-1). The temperature profiles at these stations suggested that considerable interleaving and mixing of water types had occurred, which was also evident in the T/S diagrams, which indicated mixing of ACC waters with coastal waters originating from Bransfield Strait or the Weddell Sea. There was no significant correlation between integrated Chl-a values and the profiles of upper water column stability or the depth of the upper mixed layer. The spatial variability in phytoplankton biomass within the Scotia Sea is discussed in relation to the hypothesis that low iron concentrations are the major factor controlling phytoplankton biomass in these pelagic Antarctic waters and that concentrations of iron available for phytoplankton uptake are strongly influenced by fronts and the mixing of different water masses