Distribution of chaetognaths in the central part of the Drake Passage

Abstract

The mesoscale distribution of two chaetognath species, Eukrohnia hamata and Sagitta gazellae, found in the Drake Passage in October and November of 2008 was studied using a stationary grid in the area of the Antarctic Polar Front. The distance between the stations was around ten miles. The most abundant chaetognath species was Eukrohnia hamata, which accounted for 86.7% of all the individuals collected. In the upper 200 m, the average abundance of chaetognaths decreased from 2.1 to 0.8 ind./m3, and their average biomass decreased from 1.25 to 0.25 mg/m3 over the transition through the front from the north to the south. The high heterogeneity of the spatial chaetognath distribution in the area was demonstrated: the abundance of the chaetognaths could increase or decrease over 20 miles by a factor of 45 (6.8 and 0.15 ind./m3). In addition, two peaks were revealed in the size structure of the E. hamata population, probably indicating two periods of reproduction in this species in the Drake Passage.