Scientific observations on fishes incidentally caught during commercial krill fisheries by F/V Niitaka Maru (3910t) were made from 16 December 2000 to 26 January 2001 in the vicinity of the South Shetland Islands. Among 103 net hauls quantitatively examined, by-catch fishes were found in 41 trawl catches. Lepidonotothen larseni was the most abundant in number and weight and occurred in 20.4% of hauls sampled for by-catch and 51.2% of those contained fish. P. antarcticum and C. gunnari were the second in abundance in number and weight respectively. Most hauls were dominated by one species which constitute 63.4% of hauls contained by-catch fish and a high degree of spatotemporal dissociation among juveniles of different species was recognized. The by-catch data of the present survey provided a clear picture of the negative correlation between abundance of by-catch fish and the krill CPUE. The relationship between towing time and estimated individual number of by-catch fish in each haul was obscure.