The mesh selectivity of gill net for Japanese sandfish (Arctoscopus japonicus) caught in the East Sea, Korea was described. The experiment was conducted with five different kinds of mesh size (39.4, 45.5, 51.5, 53.0, 57.6mm) between November and December 2006 in spawning season. The catch was mostly Japanese sandfish (93.3%) and some others (6.7%), and almost all of the female Japanese sandfish were larger than the fork length at 50% maturity (16.7cm). The selection curve for the female Japanese sandfish caught from the experiments was fitted by the Kitahara's method to a polynomial equation which was s(R)=exp{(0.2584R3-5.3445R2+32.269R-59.868)-0.6585} where R＝l/m, and l and m are fork length and mesh size, respectively.

The purpose of this study is to investigate the differences fatty acids and hormonal parameters in the spawning and non-spawning season between the diploid and induced triploid Far Eastern catfish, Silurus asotus. The measured triploids were produced by cold shock for 50 min at 4℃ in May 2014, the spawning season of diploid was in May, and the nonspawning season was designated in January. Estradiol and testosterone and gonadosomatic index of diploid were higher than those of induced triploid in spawning season (P<0.05), and those of diploid in spawning season were higher than nonspawning season. On the other hand, thyroid stimulating hormone and thyroxine of induced triploid were higher than those of diploid in spawning season (P<0.05). Erythrocyte count of diploid was higher than that of induced triploid in spawning season and non-spawning seasons. Mean corpuscular volume and mean corpuscular hemoglobin of induced triploid were higher than those of diploid in both seasons (P<0.05). Percentages of total saturated fatty acids and n-3 polyunsaturated fatty acids of induced triploid were higher than those of diploid in spawning season, but those of diploid were higher in non-spawning season (P<0.05). Percentages of total mono unsaturated fatty acids and total n-6 polyunsaturated fatty acids of diploid were higher than those of induced triploids in spawning season, while those of induced triploid in non-spawning season were higher (P<0.05). Therefore, induced triploids in the spawning season tend to concentrate on growth and lipid-synthesization, whereas, diploids concentrate on reproduction and gonadal maturation rather than on growth. In non-spawning season, growth and lipid- synthesization were not significantly different between diploid and induced triploid.