Spatial distribution of Pleuragramma antarcticum (Pisces: Nototheniidae) near the Filchner- and Larsen ice shelves (Weddell sea/antarctica)

Summary

In the zooplankton collected during three German Antarctic expeditions to the southern Weddell Sea in 1979/80, 1980/81 and 1983, the post-larvae of the nototheniid fish Pleuragramma antarcticum were found in 71–94% of the samples and represented 85–98% in numbers of all fish caught. In 1983, the abundance of post-larvae was up to 88 ind./m² (corresponding to 3 ind./m³). Highest concentrations were generally found over the continental slope and innershelf depressions. More than 70% of the post-larvae were caught in the upper 50–100 m water layer, in the well stratified “Summer Water” of -1.3 to -0.5°C. The Summer Water is shifted towards the outer edge of the shelf by Ekman transport and accumulation of post-larvae in the slope front and eddies can be explained by this drift. Older Pleuragramma antarcticum of age 1 resemble in their vertical distribution the juveniles and adults, 40–60% of which were caught on the shallower parts of the shelf in cold “Ice Shelf Water” of -1.8 to -2.1°C in depths below 200 m. Mean abundances of the yearclasses varied by a factor of 16 in age 0 fish and by factor of 10 in age 1. The size of a yearclass may be related to the varying appearance and persistence of an ice free coastal polynya.