In the Division 58.4.1 there are two stocks of Dissostichus mawsoni; one extends from the SSRU 58.4.1C to the SSRU 58.4.2A, and the other one to the SSRU 58.4.1H. The population sizes were vulnerable with a big range of about 1,000-2,000 t per SSRU in 58.4.1. However, there is not enough data and information to assess the stocks and deliberate proper measurements for sustainable utilize such as for precautionary catch limits. Therefore, the Korean scientists and fishing company (Insung Co.) submitted cooperatively the research plan for the exploratory longline fishery for Dissostichus spp. in SSRUs of 58.4.1 C and E using the fishing vessel, No. 3 Insung belonged to Insung Corporation during the CCAMLR meetings in 2012 to collect the fishing, biological and ecosystem data for the robust stock assessment.
The scientific research plan was carried out barely only in SSRU 58.4.1C-a and C-b during 2012/2013 season because of the harsh sea condition, even though the plan was set to conduct in 58.4.1 C-a and C-b, and E-a and E-b. The research vessel arrived in SSRU 58.4.1E-b and E-a, but we could not set even a fishing gear due to the very bad ice condition. In SSRU 58.4.1 C-b, we made five sets of each fishing gear of trotline and Spanish line, and caught only two D. mawsoni by trot line during 19-21, February. In SSRU 58.4.1C-a, we caught 30 D. mawsoni by five sets of Spanish line and 56 D. mawsoni by six sets of trot line. We could not make even sets of the two fishing gears because of the limit fishing area to operate due to the severe sea condition. The CPUE of D. mawsoni was 0.077 kg/hook and 0.144 kg/hook for Spanish line and trot line, respectively. However, it was not enough data to compare catch rate between Spanish line and trot line. The highest CPUE by fishing depth was 1,500-1,700 m. The CPUE of the fish by Pacific herring bait was higher than that for humboldt squid bait. The tagging rate was over 9.47 fishes per tonnage of green weight, and the tagging overlap was 82.3%. The average length for the male was 128.4 cm, and the female was 136.1 cm. The equation of relationship between weight and length for the male was calculated, as W = 0.000004L3.244, and for the female W = 0.000003L3.299. The dominant prey item was fishes composing of 88.67% of frequency of occurrence with 65.00% by the numbers and 88.67% by the weight, and 90.23% of IRI in the diet. The female ratio in the 84 fishes was 0.54 displaying the tendency increased with the total length became larger. The gonadosomatic index of D. mawsoni was 2.6 for the female and 1.1 for the male. The most of females and males were in maturing stage. Based on the results driven by the histological methods the spawning season was presumed from May to June, and D. mawsoni may spawn two or three times in a spawning period in SSRU 58.4.1C-a. To make clear all of the results mentioned above, reanalysis should be carried out with more data, information and samples.