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The present study investigated the virulence and expression of innate immunity genes in isolates of infectious hematopoietic necrosis virus (IHNV) in Gangwon province, South Korea, by challenging rainbow trout, Atlantic salmon, and coho salmon. Eight IHNV isolates were used to infect RTG-2 cells for viral replication using plaque assays. Three isolates with the highest replication rates, the RtPc0314g and RtPc0314c isolates of the JRt-Shizuoka type and the RtPc0816g isolate of the JRt-Nagano type, were experimentally infected into the fish. In rainbow trout, both RtPc0314c and RtPc0314g isolates showed 100% cumulative mortality while the RtPc0816g isolate showed 60% cumulative mortality for 14 days. In contrast, all three isolates showed

The ability of enriched live food, such as Artemia, to improve the growth performance of Pacific cod (Gadus macrocephalus) larvae during larviculture has yet to be fully established. Thus, the effects of feeding differentially enriched Artemia to Pacific cod larvae were investigated here, specifically the effects on the survival, growth, fatty acid composition, and air exposure stress response of the larvae. Three different commercial Artemia enrichment emulsion oils were used: commercially available enrichment 1, 2, and 3, referred to as ER1, ER2, and ER3, respectively. Although ER2-treated Artemia contained the most eicosapentaenoic acid (EPA) and ER3-treated Artemia contained the most docosahexaenoic acid (DHA) and highly unsaturated fatty acid (HUFA), the ER1 enrichment improved overall survival, growth, and survival after air stress test to the greatest extent in larval Pacific cod. Furthermore, the levels of DHA and HUFA observed in larvae fed the ER1 diet were higher than the respective concentrations of these nutrients observed in larvae fed the other diets. Thus, under the experimental conditions applied in the present study, ER1 provided Artemia with DHA and EPA ratio of 4.1 for early feeding of Pacific cod larvae.

The effect of dietary substitution of Undaria pinnatifida with carrot leaf by-product (CLB) on the growth performance and soft body composition of juvenile abalone (Haliotis discus) was determined. A total of 1080 juvenile abalone were randomly distributed into 18 cages (60 per cage). Five formulated diets and dry U. pinnatifida were prepared in triplicate. The 20% U. pinnatifida was included in the control (CLB0) diet. The 25, 50, 75, and 100% of U. pinnatifida were substituted with an equal amount of CLB, referred to as the CLB25, CLB50, CLB75, and CLB100 diets, respectively. Finally, dry U. pinnatifida was prepared to compare the effect of formulated diets on growth performance of abalone. Abalone were fed with one of the experimental diets once a day at a satiation level with a little leftover for 16 weeks. Water stability of dry matter content in all formulated diets was changed over all the observation periods, and their significant interaction was also observed. The retention of dry matter content in all formulated diets was significantly (P 0.05) different from those of abalone fed the CLB0 diet. Shell height, width, and length of abalone fed all formulated diets were significantly (P

An 8-week feeding trial was conducted to investigate the effects of dietary protein level on growth performance, feed utilization, body composition, plasma chemistry and antioxidant parameters of juvenile walleye pollock (Gadus chalcogrammus). Two-hundred and forty juvenile pollock, averaging 4.5 g, were randomly distributed between 12 400-L flow-through circular tanks (20 fish per tank). Four experimental diets with increased crude protein levels (40, 45, 50, and 55 %) were formulated, and referred to as the P40, P45, P50, and P55 diets, respectively. Each diet was assigned to three tanks and the fish were hand-fed to satiation twice daily. At the end of feeding trial, weight gain and specific growth rate increased with increasing dietary protein up to 50 %, and then decreased with further increase in dietary protein. The feed intake of the fish fed the lowest protein diet (P40) was greater than those of fish fed the higher protein diets (P45, P50 and P55). The feed efficiency was the lowest in the P40-fed fish. The protein retention tended to increase with dietary protein, from P40 to P45, and then decline when the dietary protein level was further increased to P55. The whole-body composition, except for the crude protein content, was not affected by the dietary protein content. Antioxidant response was also not affected by the dietary protein content. In conclusion, based on a second-order polynomial regression analysis of weight gain, the optimum dietary protein level for juvenile pollock was estimated to be 48.2 %.

A feeding trial was conducted to assess the effect of dietary inclusion of various aquatic animal protein sources on growth performance, feed utilization, body proximate composition, and plasma chemistry in grower walleye pollock (Gadus chalcogrammus, Pallas 1811). A total of 180 grower fish averaging 154.0 g in weight were chosen randomly and distributed into 12 flow-through tanks of 300 L (15 fish per tank). Four experimental diets were prepared in triplicate. Pollock meal (PM), anchovy meal (AM), krill meal (KM), and jack mackerel meal (JM) were used as the main protein source in the experimental diets, denoted PM, AM, KM, and JM diets, respectively. These diets were fed to fish twice a day at a satiation level for eight weeks. The weight gain and specific growth rate (SGR) of fish fed the KM and JM diets were higher than were those of fish fed the other diets. Daily feed intake (DFI) and daily protein intake (DPI) of fish fed the KM and JM diets were higher than were those of fish fed the PM and AM diets. The strong second polynomial correlation between the contents of 4 free amino acids (arginine, glutamic acid, histidine and leucine) in protein sources and WG, SGR, DFI and DPI were observed. The experimental diets had no effect on proximate composition of the muscle and liver. Plasma analysis did not differ between the experimental diets. In conclusion, KM and JM showed the greatest protein sources than among the ingredients assessed, and consequently KM and JM yielded the higher growth (WG and SGR) and feed intake (DFI and DPI).

We evaluated effects of dietary lipid level on growth performance, feed utilization, fatty acid composition, plasma chemistry, and antioxidant responses in juvenile walleye pollock (Gadus chalcogrammus). Two-hundred forty juvenile pollock averaging 4.4 g in weight were randomly distributed between 12 400-L flow-through circular tanks (20 fish per tank). Fish were fed four isonitrogenous experimental diets with crude lipid levels of 8.1%, 12.6%, 16.7%, or 20.8% for 8 weeks. Each diet was assigned to three tanks, and the fish were hand-fed to satiation twice daily. At the end of the trial, weight gain, specific growth rate, feed efficiency, and protein efficiency ratio were increased with increasing dietary lipid up to 16.7%, and then decreased with a further increase in dietary lipid. The hepatosomatic index showed an increasing trend with increasing dietary lipid. The crude lipid content in liver increased with increasing dietary lipid. Saturated fatty acid levels in the muscle and liver decreased, whereas essential fatty acids and polyunsaturated fatty acids in the muscle and monounsaturated fatty acids in the liver increased with increasing dietary lipid. The hematological and antioxidant parameters were not affected by the dietary lipid content. In conclusion, on the basis of a second-order polynomial regression analysis of weight gain, the optimum dietary lipid level for juvenile walleye pollock was estimated to be 15.8%.

This study examined the influence of water temperature on the induction of vitellogenin (VTG) in walleye pollocks (Gadus chalcogrammus) in aquaculture. The full-length VTG-A (or VTG-I) gene of walleye pollock was cloned using RACE (Rapid amplification of cDNA ends)-PCR method from liver tissue and recombinant VTG protein (wpVTG) was expressed in E. coli. The wpVTG protein was used to construct polyclonal antibodies to specifically detect VTG in blood; the antibodies were verified using western blotting. The VTG in blood plasma was determined by ELISA. The relationship between GSI (gonadosomatic index), VTG and body length were all positively correlated, and the results indicated that VTG can be used as an indicator of sex and/or maturation of female G. chalcogrammus in aquaculture. When VTG was measured in by the aqua-cultured female pollocks raised in water temperature of 5 °C, 8 °C, 11 °C, and 14 °C, VTG was detected only at 5 °C and 8 °C. In the histological analysis of VTG-inducing individuals, vitellogenesis was found in ovaries. In those same samples, E2 (17beta-estradiol) was detected in the blood by LC-MS. On the other hand, there was no significant difference in level of VTG induction when E2 of same concentration was treated to hepatocyte culture in different water temperatures. These results seemed to indicate that VTG is not directly affected by water temperature. However, we considered that the water temperature indirectly affect VTG induction by affecting the E2 concentration level.