Breeding takes place in at least four areas : the Bellingshausen Sea, the Brans-field Strait, Davis Strait, and in the vicinity of South Georgia Island. We do not know whether there is a main breeding area in the Pacific Sector or how many breeding stocks there are. A female krill produces from as few as 500 eggs to as many as 8,000 eggs (average of 2,500) per brood with a brood interval of 6.5 days. The spawning season lasts two months, yielding an annual egg production of 22,000 eggs per season per female (Ross and Quetin, 1983). Early larval stages readily become acclimatized to high pressure conditions of up to 200 atm., while adult krill, including gravid females, are sensitive to pressure and can acclimatize only to 20 atm. Spawning cannot therefore occur at depths greater than 200 m. Krill egg development is also influenced by temperature but not by salinity or hydrostatic pressure.
While our knowledge of krill spawning and hatching in the shelf areas has increased in recent years, virtually nothing is known about the fate of eggs spawned over oceanic depths. We do not know, for instance, how deep these eggs will sink or at what depth the very early larval development takes place.
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