Some aspects of biology and ecology of krill (Euphausia superba), Bransfield Strait and Elephant Island, austral summer 2007 (ANTAR XVII).

Abstract

Results are described of some biological and ecological aspects of the Antarctic krill along Bransfield Strait and Elephant Island (First phase) as well as between Elephant and Clarence Islands (Second phase), conducted on board the RV Humboldt from January 17th to 23rd 2007, with the goal to know the distribution, size composition, sex ratio, length-weight, feeding intensity and diet. Twenty-five fishing hauls were made: 13 were for the first phase and 12 to the second. The total catch was 6,852 kg of which 99% corresponded to Antarctic krill. The vertical distribution was shallow between 25 and 50 m of depth; otherwise on Elephant and Clarence Islands were located deeper (50-75 m). The size structure of E. superba showed two modes, one of them made up by sub adult individuals (43 mm of total length-TL) and juveniles (28-30 mm TL). By areas, juveniles were representative in Bransfield Strait and Ocean Front whereas, adults’ mainly gravid females with higher body weight were found at Elephant and Clarence Islands. Between 04:00 and 12:00 hours, individuals were moderate and intensively fed while between 16:00 and 20:00 hours, slightly fed. The krill diet was constituted by phytoplankton elements (diatoms, dinoflagellates and tintinnids). No significant differences were observed in the krill diet regarding the sizes, time of day and depth of catch.