Maturity and spawning of the Octopus longispadiceus was investigated based on the samples collected in the East Sea. We analyzed monthly changes in maturity stage, gonadosomatic index (GSI), eggs diameter, fecundity and body weight at group maturity. Mature stages appeared every month, and GSI values were high every month. Spawning season was estimated to be year-round, and main spawning occurs intensively in sping and fall. The eggs diameter of mature stage was 19.2 ± 3.0 mm. The total number of eggs in the fecundity ranged from 31 eggs in 189 g (BW) to 184 eggs in 1,013 g (BW), which was proportional to body weight (BW), and the relationship between total weight and fecundity was F = 0.7593 × BW0.7719 (R2 = 0.7462). The percentages of sexually mature females estimated using a logistic equation were over 50% at 323.4 g BW, 75% at 451.4 g BW and 97.5% at 750.3 g BW, respectively. We think that it be good way for Octopus longispadiceus to be regulated by fishing gear and fishing method.

This study aimed to identify the selectivity of catches according to mesh size of gillnets, and to collect basic data for fisheries resource management plans for gillnets. The mesh selectivity test was conducted with five different mesh sizes (60, 66, 69, 75, and 96 mm) gillnet in coastal sea of Mukho port and the selectivity was analyzed using the Kitahara method. In results of the selectivity test, a total of 143 (36,249 g) of atka mackerel were caught and the 60 mm gillnet was the highest at 83 (18,596 g), which is about 58.0% of the total catch. The relative growth equation between body length and weight showed that weight tends to increase proportional to body length. The maximum length/mesh size value was showed 0.490 by the master curve of selectivity, and the 50% selection range was showed 0.138. Therefore, it was found that the size of the caught fish increased proportional to the mesh size. The results of this study were intended to be used as data for establishing a plan for efficient management of atka mackerel resources.

The purpose of this study is to compare the ichthyofauna between the eelgrass bed waters located in the open sea and the nearby sea free of eelgrass, and this study collected a total of 26 species. Comparing the fish collected on the eelgrass bed (St.2) of Geomun–do coast with the fish collected on the coastal waters (St.1) void of the nearby eelgrass bed, the fish collected from the eelgrass bed included 19 species, 413 individual with 16,110.6g in weight while the fish collected from the coastal waters void of the eelgrass bed included 19 species, 290 individuals with 12,961.5g in weight. Accordingly, it was found that the population size and biomass of the fish collected from the eelgrass bed were higher than the coastal waters void of the eelgrass. This study could identify that diversity, richness, evenness index except dominance were also much higher even in the result of cluster analysis.