Migrations of Antarctic fish Pseudochaenichthys georgianus Norman, 1939 in the Scotia Sea

The material obtained between 1986 and 1991 has allowed to study the pattern of geographical and depth distribution of Pseudochaenichthys georgianus in the area of Scotia Arc Islands and on shelf of South Georgia Island. In the Antarctic colder waters in the Palmer Archipelago there were mostly young, small fishes. They have stomach filled well with krill so swim probably to match with distribution of krill, which flow further to North and East with geostrophic currents. Following after them, with stomach often full of them, they became large, so the numbers of small individuals are disappearing farther from continent. Their gonad are more developed as the temperature further from continent get warmer. Finally at the end of Scotia Arc Islands - at South Orkney, P. georgianus are large with gonad ready to spawn, and mostly concerning on reproduction, they do not feeding, so they do not have reason to follow after krill driven to the East to deep open Scotia Sea.



In vast Antarctic Zone, enlarged by ice cover species are distributed into age groups separated geographically: first age group as was not in sampled area, have to be assumed to be near or under ice feeding on juvenile krill and fish; age 2 with 3 are in the South Shetlands; age 4+ are accumulating at South Orkney. While on shelf of one, small sub-antarctic island the group ages of P. georgianus are by time separated in a patterns of strong – week cohorts: age group of 4 is separated from the 2th by low numbers fish in previous age group 3. This may save them before feeding of own younger fish – common fish behavior among predators.



At South Orkney there are no small fishes. After hatching in cold winter waters as coming summer warm them, they swim upstream (as young fish usually do) to colder water of Palmer Archipelago to have more efficiency in food assimilation. This behavior save them before to be driven to open pelagic water and ensure good reproductive success as old fish drifting to warm water to gonad develop and to spawn.



At South Georgia similar pattern exist in the distribution of P. georgianus. Large specimens were closer surface near Eastern shores of South Georgia where water is warmer and sheltered before to be driven to Eastern large pelagic sea. After spawn young postlarvae swim upstream to the West, to the deep and cold waters. Spawning, feeding, diurnal and another migrations means changes of environments and physiology - events that have appropriate marks in the otolith microstructure.