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In flounder aquaculture, selective breeding plays a vital role in the development of disease-resistant traits and animals with high growth rates. Moreover, superior animals are required to achieve high profits. Unlike growth-related traits, disease-resistant experiments need to be conducted in a controlled environment, as the improper measurement of traits often leads to low genetic correlation and incorrect estimation of breeding values. In this study, viral hemorrhagic septicemia virus (VHSV) resistance was studied using a genome-wide association study (GWAS), and the genetic parameters were estimated. Genotyping was performed using a high-quality 70 K single nucleotide polymorphism (SNP) Affymetrix® Axiom® myDesign™ Genotyping Array of olive flounder. A heritability of ∼0.18 for resistance to VHSV was estimated using genomic information of the fish. According to the GWAS, significant SNPs were detected in chromosomes 21, 24, and contig AGQT02032065.1. Three SNPs showed significance at the genome-wide level (p 1 × 10

We investigated the underwater shapes of trolling lines for the improvement of hairtail fishing efficiency. Two sets of experiments were carried out, one on a small scale, where flume tank tests of four models were scaled down by a ratio of 1:10 and trolled at different speeds, and another at full scale, comprising a survey on board a commercial fleet. In situ trials were conducted off the coast of Jeju Island, South Korea, at 33°27′57.528″N, 126°55′48.846″E, a potential fishing ground for hairtail fishing. The full-scale gear was set by altering sinker weights whilst changing the length of the warp line at different towing speeds. A dynamic method using a mass-spring technique and full-scale gear was developed. External and internal forces that govern the motion of the gear were considered. A non-linear differential equation of motion was developed, solved by a fourth-order Runge–Kutta method at a time step of 5 × 10−4 s for each trial. A static method was also developed using full-scale gear to predict the equilibrium gear configuration under all fishing conditions. The dynamic method better predicts the actual underwater performance of trolling line gear in real time.

Dietary substitution effect of sea tangle (ST) with rice bran (RB) on growth and carcass composition of juvenile abalone (Haliotis discus) was determined. Juvenile abalone was acclimated to the experimental conditions for 4 weeks. Seventy juvenile abalone averaging 0.43 g were randomly distributed into each of the 18, 70 L plastic rectangular containers. The experimental diets were fed to abalone once a day at a satiation level with a little leftover. The feeding trial lasted for 16 weeks. Survival of abalone was not affected by dietary substitution of ST with RB. However, weight gain of abalone fed the RB40 diet was higher than that of abalone fed the all other diets except for the RB0 diet. No significant difference in weight gain was found in abalone fed between the RB0 and RB100 diets. SGR of abalone fed the RB40 diet was higher than that of abalone fed the all other diets. Also SGR of abalone fed the RB0 diet was higher than that of abalone fed the RB100 diet, but not different from that of abalone fed the RB20, RB60 and RB80 diets. Moisture, crude protein and ash content of the soft body of abalone were affected by dietary substitution of ST with RB. In conclusion, the 100% ST could be substituted with RB without a retardation of weight gain of abalone when the 20% ST was included into the experimental diet. However, the best growth performance was obtained in abalone fed the RB40 diet substituting 40% ST with RB.

The effects of dietary substitution of fishmeal with the combined dry Nannochloropsis oceanica (NO) biomass residue and casein on growth performance and carcass composition of juvenile abalone was determined. One thousand two hundred and sixty juvenile abalone were randomly distributed into the 18 L plastic rectangular containers. Five experimental diets in triplicate were prepared. The 28% fishmeal was included into the control (Con) diet. The 25%, 50%, 75% and 100% fishmeal were substituted with the combination of graded levels of dry NO biomass residue and casein, referred to as the NO25, NO50, NO75 and NO100 diets respectively. Finally, the salted sea tangle (ST), Laminaria japonica was prepared to compare the effect of the experimental diets on performance of abalone. The essential amino acids, such as isoleucine, leucine, phenylalanine, threonine and valine tended to increase with dietary substitution of fishmeal with NO biomass residue in the experimental diets. Arginine tended to decrease with dietary substitution of fishmeal with NO biomass residue. Survival of abalone fed the experimental diets was higher than that of abalone fed the ST diet for 16 weeks. Weight gain and specific growth rate (SGR) of abalone fed the NO100 diet were higher than those of abalone fed the all other diets. Weight gain and SGR of abalone linearly increased with dietary substation of fishmeal with NO. Shell length of abalone tended to increase with dietary substitution of fishmeal with the combined dry NO biomass residue and casein. The chemical composition of the soft body of abalone was different among treatments except for moisture content. In conclusion, fishmeal in the diets for abalone could be completely replaced with the combined dry NO biomass residue and casein when the 28% fishmeal was included.

The migrating behaviour of fish schools such as jack mackerel Trachurus japonicus, spotted mackerel Scomber australasicus, and Japanese anchovy Engraulis japonicus was investigated in set-net fishing grounds by means of sonar image records. The spotted mackerel and Japanese anchovy schools moved at an average speed of 18-19cm/s, while the jack mackerel schools moved at 29cm/s. Schools of all species changed their direction of movement at an average veering angle of 19 ?? 36°. However, the veering angle of Japanese anchovy schools showed a tendency to be larger than that of the other two species. The average duration of straight movement of the spotted mackerel and Japanese anchovy schools was 2 ?? 2.4min, while that of the jack mackerel schools was 2.9min. This confirms a frequent veering of fish schools in the set-net fishing grounds. The jack mackerel and Japanese anchovy schools tend to move along the isobathic route with a depth change ratio of 0.6 ?? 0.8m/min between the first and final image. In case of the spotted mackerel schools the larger depth change was observed up to 6m/min.

Water tank experiments on fish behaviour towards model nets were conducted using tilapia Oreochromis niloticus to compare the leading effects between a straight leader-net and a leader-net with Kaeshi-ami. The difference in leading effects between the two different types was evaluated by the swimming distance along the leader-net and the leading rate of the leader-net. The results showed that the swimming distance along the leader-net with Kaeshi-ami was much longer than that of the straight leader-net. The leading rates of the straight leader-net and leader-net with Kaeshi-ami were 12% and 48%, respectively. Moreover, it was sug-gested that improvements in the construction of Kaeshi-ami can increase its leading effect.