Hyeonho Yun

Effects of Feeding Rate and Water Temperature on Growth and Body Composition of Juvenile Korean Rockfish, Sebastes schlegeli (Hilgendorf 1880)

Three feeding trials were conducted to evaluate the effects of feeding rate and water temperature on growth and body composition of juvenile Korean rockfish, Sebastes schlegeli rearing at 3 different water temperatures. A total of 270 fish (each experiment) individual body weight (BW) averaging 16±0.3 g (mean±SD) were fed a commercial diet for 4 wk at 16°C, 20°C, and 24°C. At each temperature, triplicate tanks were assigned to one of 6 feeding rates: 1.5%, 2.5%, 2.8%, 3.1%, 3.4%, and satiation (3.7% BW/d) at 16°C, 1.9%, 2.9%, 3.2%, 3.5%, 3.8% and satiation (4.1% BW/d) at 20°C and 1.7%, 2.7%, 3.0%, 3.3%, 3.6%, and satiation (3.9% BW/d) at 24°C water temperature. Weight gains of fish in satiation and 3.4% groups at 16°C, in satiation and 3.8% groups at 20°C and in satiation and 3.6% groups at 24°C were significantly higher than those of fish in the other treatments (p<0.05). A broken line regression analysis of weight gain indicated that optimum feeding rates of juvenile Korean rockfish were 3.41% at 16°C, 3.75% at 20°C and 3.34% at 24°C water temperature. Results of the present study indicate that the optimum feeding rate could be >3.1% but <3.41% at 16°C, >3.5% but <3.75% at 20°C and >3.0% but <3.34% at 24°C. As we expected results suggest that fish performed better at 20°C than 16°C or 24°C water temperature and the optimum feeding rate could be 3.1% BW/d to 3.7% BW/d in 16 g of juvenile Korean rockfish.

Effects of Salinity Changes on Hematological Responses in Juvenile Ship Sturgeon Acipenser nudiventris

A 10-day trial was conducted to evaluate the salinity tolerance and hematological responses of juvenile ship sturgeon Acipenser nudiventris under different salinity levels. A total of 240 fish averaging 6.2 ± 0.13 g (mean ± SD) were randomly distributed into 12 tanks in groups of 20, and each tank was then randomly assigned to one of three replicates of four different salinities at 0, 4, 8 and 12‰. At the end of 10 days of experimental period, plasma protein value of fish exposed to 0‰ and 4‰ salinities was signifi cantly higher than those of fish exposed to 8‰ and 12‰ salinities ( P < 0.05). Significantly higher values for plasma cortisol and glucose were obtained in fish exposed to 12‰ salinity compared to the fish exposed to 0‰ and 4‰ salinities ( P < 0.05). Plasma potassium and sodium values increased significantly by increment of salinity levels ( P < 0.05). Therefore, these results indicated that in natural environments, juvenile ship sturgeon, A. nudiventris in migratory populations could be able to migrate and adjust successfully into brackish water with a salinity of up to 8‰ without any short-term hematological stress responses.

The dietary valine requirement for rainbow trout, Oncorhynchus mykiss, can be estimated by plasma free valine and ammonia concentrations after dorsal aorta cannulation

This study was carried out to evaluate the dietary valine requirement by measuring means of the plasma free valine and ammonia concentrations in rainbow trout, Oncorhynchus mykiss, after dorsal aorta cannulation. A total of 35 fish averaging 498±7.2 g (initial body weight, mean±SD) were randomly distributed into seven groups with five fish in each group. After 48 h of feed deprivation, each group was fed one of seven L-amino acid based diets containing graded levels of valine (0.45, 0.95, 1.20, 1.45, 1.70, 1.95 or 2.45% of diet, dry matter basis) by intubation at 1% body weight. Blood samples were taken at 0, 5 and 24 h after intubation. Post-prandial plasma free valine concentrations (PPval, 5 h after intubation) and post-absorptive free valine concentrations (PAval, 24 h after intubation) of fish fed diets containing 1.45% or more valine were significantly higher than those of fish fed diets containing 1.20% or less valine (P<0.05). Post-prandial plasma ammonia concentrations (PPA, 5 h after intubation) remained low or constant from fish fed diets containing 0.45–1.45% valine, but increased linearly from fish fed diets containing 1.45–2.45% valine. Post-absorptive plasma ammonia concentrations in the present study were not significantly different among the groups. Broken-line model analyses on PPval, PAval and PPA indicated that the dietary valine requirements of rainbow trout was between 1.41 (3.85) and 1.50% (4.10) of diet (% of dietary protein on a dry matter basis).

Evaluation of dietary soybean meal as fish meal replacer for juvenile whiteleg shrimp, Litopenaeus vannamei reared in biofloc system

Different levels of dietary soybean meal (SBM) as a fish meal (FM) replacer, with and without amino acid supplementation, for whiteleg shrimp, Litopenaeus vannamei reared in the biofloc system was examined in eight weeks of feeding trial. Eight experimental diets consisted of a basal diet with 0% FM replacement by SBM provided in clear sea water without biofloc system (S0SW), four diets replacing FM at 0% (S0), 33% (S33), 67% (S67) and 100% (S100) by SBM, and three diets replacing FM at 33% (S33A), 67% (S67A) and 100% (S100A) by SBM supplemented with amino acids (methionine and lysine) in the seawater biofloc system. Results of water quality analyses showed significantly lower total suspended solids and nitrate for S0SW group than all other treatments. Diets S0 and S33A resulted in higher weight gain and specific growth rate among all groups, with no significant differences with S33 group. In addition, whole-body protein and amino acid compositions of shrimp fed S0SW were lower than most biofloc groups. Haemolymph parameters showed significant differences in total protein, cholesterol and triglyceride between groups S0 and S0SW. Also, superoxide dismutase activity showed a decreasing trend with increasing replacement level. In conclusion, based on these results, SBM could replace up to 33% of FM with or without amino acid supplementation in juvenile whiteleg shrimp diets reared in the biofloc system.

Dietary vitamin C reduced mercury contents in the tissues of juvenile olive flounder (Paralichthys olivaceus) exposed with and without mercury.

A 2×3 factorial design was employed to evaluate the effects of dietary vitamin C (l-ascorblyl-2-monophosphate, C2MP) levels on growth and tissue mercury (Hg) accumulations in juvenile olive flounder, Paralichthys olivaceus. Six experimental diets with two levels of mercuric chloride (0 or 20mg HgCl2/kg diet) and three levels of vitamin C (0, 100, or 200mg C2MP/kg diet) were added to the basal diet. At the end of 6 weeks feeding trial, in presence or absence of dietary Hg, fish body weight gain, specific growth rate, feed efficiency, protein efficiency ratio and whole body lipid content were increased in a dose-dependent manner as dietary vitamin C level increased in the diets. Interestingly, fish fed 100 or 200mg C2MP/kg diets showed significant interactive effects on reducing Hg content in kidney tissue. These results revealed that dietary vitamin C as 100 or 200mg C2MP/kg diet had protective effect against Hg accumulation in juvenile olive flounder.

Additives in aquafeed: An overview

Additives in aquafeed are nutritive/nonnutritive ingredients that are supplemented in small amounts (alone or in combination) for a specific purpose, such as to improve the quality of fish as a final product, to preserve the physical and chemical quality of the diet, or to maintain the quality of the aquatic environment. Moreover, growing interest in raising fish in an antibiotic-free environment, driven by consumer interest in the quality and safety of seafood, has hastened the search for safe dietary immunostimulants as an alternative to antibiotics. However, the importance of these additives received little attention outside the purview of aquaculture researchers. This chapter reviews the use of substantially important and promising additives in aquafeed.

Optimal Feeding Frequency for Juvenile Korean Rockfish Sebastes schlegeli Fed Commercial Diet at Two Different Water Temperatures

We conducted two feeding trials to investigate the optimal feeding frequency of juvenile Korean rockfish Sebastes schlegeli fed a commercial diet of expanded pellets containing 47.2% crude protein, 9.2% crude lipid, and 14.5% ash at two different water temperatures. In the first experiment, triplicate groups of 20 fish with an average weight of 2 g were fed an equal amount of diet (5.97% based on body weight) at one of six feeding frequencies (2, 3, 4, 5, 7, or 9 meals/day) for four weeks at . After four weeks, we measured weight gain (WG), specific growth rate (SGR), feeding efficiency (FE), and protein efficiency ratio (PER). Fish fed diet five meals/day grew significantly better than those fed nine meals/day. The second experiment used identical experimental conditions and feeding regions, except the food ration was slightly less (5.92% based on body weight) and the water temperature was increased to . After four weeks, we again measured WG, SGR, FE and PER. Fish fed seven meals/day grew significantly faster than those fed 2, 3, 4, or 9 meals/day. Whole-body protein levels in fish fed three meals/day was higher than those fed four meals/day in water, but whole-body lipids in the fish fed four meals/day was higher than those fed two meals/day in water. A second-order polynomial analysis based on WG suggested the optimal feeding frequency for juvenile Korean rockfish was five meals/day at and six meals/day at , indicating that fish reared in higher water temperature require higher feeding frequencies.

Synergistic Effects of Dietary Vitamins C and E on Methylmercury-Induced Toxicity in Juvenile Olive Flounder Paralichthys olivaceus

Abstract This experiment was conducted to evaluate the synergistic effects of vitamin C and E on methylmercury (MeHg) toxicity in juve -nile olive flounder Paralichthys olivaceus . In a 3×3 factorial design, 9 experimental diets containing three different vitamin C (0, 200 or 400 mg/kg diet in the form of l-ascorbyl-2-monophosphate) and vitamin E (0, 100 or 200 mg/kg diet in the form of dl-α-tocopheryl acetate) levels with the Hg toxicity level (20 mg/kg diet in the form of MeHg) were formulated. Triplicate groups of fish averaging 2.3 ± 0.05 g (mean ± SD) were fed one of the 9 diets in a flow through system for 8 weeks. Fish fed 400 mg vitamin C/kg diet with 100 or 200 mg vitamin E/kg diet showed significantly ( P < 0.05) higher weight gain (WG) than did fish fed the other diets. Fish fed 400 mg vitamin C/kg diet at all vitamin E levels and those which fed vitamin C and E equally at a rate of 200 mg/kg diet showed significantly ( P < 0.05) higher feed efficiency (FE), specific growth rate (SGR) and protein efficiency ratio (PER) than did fish fed the other diets. Fish fed 200 and 400 mg vitamin C/kg diet exhibited significantly (

Optimum Feeding Rate and Frequency in Juvenile Korean Rockfish Sebastes schlegeli Fed a Commercial Diet

우리나라 주요 어류양식 어종인 조피볼락(Sebastes schlegeli) 은 2010년 생산량이 20,918톤(국내 어류양식 총 생산량의 20%)으로 국내 어류양식에서 두 번째로 생산량이 많은 어종 이다(FAO, 2012). 다른 어종과 마찬가지로 조피볼락의 생산성 및 양식경영비에서 가장 중요하게 영향을 미치는 것은 사료이 며, 총 양식경영비의 50-60%에 이른다(Cho et al., 2006). 현재 까지 조피볼락 양식의 효율적인 관리와 생산성 향상을 위해서 많은 연구들이 수행되었다. 배합사료 개발을 위해 영양소 요구 량과 사료 원료 이용성에 관한 연구들이 수행 되었고(Lee et al., 1993; Kim and Bae, 1999), 배합사료에 의한 생사료 대체 가능 성과 같은(Lee and Jeon, 1996), 환경 친화적인 고효율 배합사 료 개발을 위하여 많은 연구들이 수행되고 있다. 하지만 조피볼 락을 비롯한 양식 어류의 성장은 사료 이외에 망갈이, 선별, 수 온 등의 외부 환경요인에 의해서 많은 영향을 받는다(Choi et al., 2009). 따라서, 양식어종에 대한 적합한 사료가 개발되더라 도 외부환경에 따른 사료공급방법이 제대로 이루어지지 않으 면 성장 및 사료효율이 달라지고, 수질오염 발생 등 많은 부작용 이 일어날 수 있기 때문에(Kim et al., 2005), 효율적인 사료공급

Dietary Sulfur Amino Acids Can Spare Taurine in Rock Bream Oplegnathus fasciatus

An 8 week feeding trial was conducted to evaluate whether methionine and cysteine would effectively spare taurine supplementation on growth performance in juvenile rock bream Oplegnathus fasciatus. Triplicate groups of 25 fish averaging 2.74 ± 0.04 g (mean ± SD) were fed one of the experimental diets. Five experimental diets including a fish meal based control diet were prepared by adding sulfur amino acid at fixed level of 1.0% and taurine at graded levels of 0%, 0.25%, 0.5% and 1.0% (S + Tau 0, S + Tau0.25, S + Tau0.5 and S + Tau1.0, respectively). After the feeding trial, growth performance of fish fed the S + Tau 0.25, S + Tau0.5 and S + Tau1.0 diets were significantly higher ( P < 0.05) than those of fish fed the Control diet. ANOVA test suggested that when sulfur amino acid were supplemented to the diets, the optimum taurine supplementation level could be 0.25% in the diet, and broken line analysis of weight gain indicated a level of 0.33%, for positive effects on growth and feed utilization. Fish whole-body protein content and taurine concentration steadily increased with the increase of dietary level in the presence of sulfur amino acid in the diets. On the other hand, whole-body lipid content significantly decreased with the incremental levels of dietary taurine. In conclusion, the results of the present study clearly indicated that dietary supplementation of methionine and cysteine at a level of 1% could spare 0.25 to 0.33% of taurine in juvenile O. fasciatus diets.