Distribution and growth of larval and adult Thy-sanoessa macrura (Euphausiacea) in the Bransfield Strait Region, Antarctica

Thysanoessa macrura was the most common euphausiid in the western Bransfield Strait region, with highest abundances of 5000 individuals per 1000 m3 in Gerlache Strait in December 1986 and 4500 ind. 1000m-3 in January 1987. w h c h coincided temporally and spatially with the annual spring bloom of phytoplankton. With the progression of the austral summer, high larval abundances extended into Bransfield Strait, apparently advected there by the Bransfield Current, estimated both geostrophically and with Lagrangian drifters. A discrete spawning period prior to December 1986 gave rise to a distinct cohort which persisted through March 1987. The study area was highly variable in phytoplankton biomass. Waters of northern Gerlache Strait reached 25 mg chl a m-3 in January 1987, whereas Drake Passage always had <2.0 mg chl a m-3 from December 1986 to March 1987 No differences in development or growth rate were found in regions with different levels of algal biomass. The development time from calyptopis 2 to furcilia 6 was ca 90 d Larvae of T. macrura did not appear to perform diel vertical migration between the 0 to 100 and 100 to 200 m depth layers.