• Journal of Aquaculture
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• v.11 no.1
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• pp.83-90
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• 1998

The effects of Obosan in the diet on growth, percent weight gain, specific growth rate, feed conversion ration and body composition of nile tilpia were investigated. First feeding fry average weighing 11.0 mg were fed the diets containing 0%, 0.25%, 0.5%, 1.0% and 2.0% Obosan for 7 weeks. Body weight, percent weight gain, specific growith rate of fish fed the diets containing 0.25%, 0.5% and 1.0% Obosan were significantly higher than control diet (P<0.05). Feed conversion ratio of fish fed the diets containing 0.25% and 0.5% Obosan showed best results compare to other experimental groups (P<0.05). Juvenile average weighing 281.0g and adult fish average weighing 563.0g were fed control and 0.3% Obosan supplemented diet for 30 days and 175 days, respectively. Body weight, percent weight gain and specific growth rate were significantly higher in the fish fed Obosan supplemented diet than control diet (P<0.05). Crude protein, crude lipid, crude ash and moisture of dorsal muscle and liver were not significantly different between two experimental groups.

• Journal of Aquaculture
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• v.14 no.3
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• pp.197-203
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• 2001

To replace fish meal (FM) in the diet of Nile tilapia, Oreochromis nloticus, different levels of Iysine cell mass (LCM) were added to diet on protein equivalent base. fish averaging 3.0 g fed one of nine diets containing isonitrogenous and isocaloric basis of 35% crude protein and 15.3kJ available energy/g diet: $LCM_0, 100% FM: LCM_{10}, 90% FM+10% LCM, LCM_{20}, 80% FM+20% LCM; LCM_{30}, 70% FM+30% LCM; LCM_{40}, 60% FM+40% LCM; LCM_{30}l, 70% FM+30% LCM+lysine; LCM_{30}ln, 70% FM +30% LCM + lysine +NaOH; LCM_{40}lan, 60% FM+40% LCM+lysine+arginine; LCM_{40}/lan, 60% FM+40% LCM+lysine+arginine+NaOH.$. After 8 weeks of feeding trial, there were no significant differences in weight gain (WG) and specific growth rate (SGR) among fish fed LCM$_{0}$ (control diet), LCM_{10}, LCM_{30}, LCM_{40}, LCM_{30}l, LCM_{30}ln, LCA_{40}la and LCM_{40}lan diets (P>0.05)$, while fishes fed $LCM_{20} diet were significantly higher than those fed LCM_{0}, LCM_{30}, LCM_{40}, LCM_{40}la and LCM_{40$}lan diets (P<0.05). There were no significant differences in feed efficiency (FE) and protein efficiency ratio (PER) among fish fed control diet, $LCM_{10}, LCM_{20}, LCM_{30}ln, LCM_{ 40}la and LCM_{40}$lan diets (P>0.05), while fishes fed control diet were significantly higher than those fed $LCM_{30}, LCM_{40} and LCM_{40}l diets (P<0.05)$. Positive effects were not shown in WG and SGR with supplementation of amino acids (lysine & arginine) and neutralizatio, while FE and PER from fish fed $LCM_{40}la and LCM_{40}lan diets were significantly higher than those fed LCM_{30}, LCM_{40} and LCM_{30}$l diets (P<0.05). Hence, LCM can replace FM up to 40%, and dietary suppl-ementacon and neutralization of amino acids showed positive effects, when FE and PER were considered in juvenile tilapia diet.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.2
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• pp.110-114
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• 2002

The study was carried out to investigate the changes of haematological constituents induced by dietary exposure of Hexachlorobenzene (HCB) and Polychlorinated biphenyls (PCBs) in nile tilapia, Oreochhromis niloticus. The nile tilapia were fed pellet with 0.05, 0.25 and 0.50 mg/kg body weight/day of HCB and PCBs for 30 days, respectively. HCB ($\ge$ 0.25 mg/kg) induced a significantly decreased the red blood cell count at 30 days, and the hemoglobin concentration and hematocrit value were significantly decreased after 20 days to 0.50 mg/kg. The diminution of red blood cell count, hemoglobin concentration and hamatocrit value by PCBs was found after 20 days at $\ge$0.25 mg/kg. The concentrations of calcium decreased significantly at 30 days at $\ge$0,25 mg/kg of PCBs-diet. However, magnesium and inorganic phosphorus did not show any noticeable changes in the range of 0.05$\~$o.50 mg/kg of HCB and PCBs compared to control group during the experimental period, The low concentration of total protein was observed at the last day of experiment to 0.50 mg/kg of HCB-diet, while total protein initiated to increase from 20 days at the 0.25 mg/kg of PCBs-diet. The glucose was significantly increased after 20 days at $\ge$0,25 mg/kg of HCB and PCBs, A significant increment GOT and GPT activities was noticed after 20 days at 0.50 mg/kg of HCB and PCBs, These results indicate that hematological and serum biochemical changes in the nile tilapia by dietary exposure to HCB and PCBs are affected at more than 0,25 mg/kg after 20 days.

• Applied Microscopy
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• v.23 no.2
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• pp.27-40
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• 1993

This study was taken to examine the light microscopic and ultrastructural changes of gill and kidney of female tilapia{Oreochromis niloticus) adapted in 0%o, 10%o, 20%o, and 30%o salt concentrations, respectively, by light, scanning and transmission electron microscope. The results obtained in these experiments were summarized as follows: Gill chloride cell hyperplasia, gill lamellar epithelial separation, kidney glomerular shrinkage, blood congestion in kidneys and deposition of hyalin droplets in kidney glomeruli, tubules were the histological alterations in Oreochromis niloticus. Incidence and severity of gill chloride cell hyperplasia rapidly increased together with increase of salinity, and the number of chloride cells in gill lamellae rapidly increased in response to high external NaCl concentrations. The ultrastructure by scanning electron microscope(SEM) indicated that the gill secondary lamella of tilapia(Oreochromis niloticus) exposed to seawater, were characterized by rough convoluted surfaces during the adaptation. Transmission electron microscopy(TEM) indicated that mitochondria in chloride cells exposed to seawater, were both large and elongate and contained well-developed cristae. TEM also showed the increased chloride cells exposed to seawater. The presence of two mitochondria-rich cell types is discussed with regard to their possible role in the hypoosmoregulatory changes which occur during seawater-adaptation. Most Oreochromis niloticus adapted in seawater had an occasional glomerulus completely filling Bowman's capsule in kidney, and glomerular shrinkage was occurred higher in kidney tissues of individuals living in 10%o, 20%o, 30%o of seawater than in those living in 0%o of freshwater, and blood congestion was occurred severer in kidney tissues of individuals living 20%o, 30%o of seawater than in those living in 10%o of seawater. There were decreases in the glomerular area and the nuclear area in the main segments of the nephron, and that the nuclear areas of the nephron cells in seawater-adapted tilapia were of smaller size than those from freshwater-adapted fish. Our findings demonstrated that Oreochromis niloticus tolerated moderately saline environment and the increased body weight living in 30%o was relatively higher than that living in 10%o in spite of histopathological changes.

• Korean Journal of Animal Reproduction
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• v.16 no.4
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• pp.377-385
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• 1993

This study was taken to examine correlationships between ehdocrine changes such as estradiol-17$\beta$, progesterone, T4 and T3 and serum components concentrations of female Oreochromis niloticus living in 0$\textperthousand$, 10$\textperthousand$, 20$\textperthousand$, and 30$\textperthousand$ salt concentrations, respectively. The results obtained in these experiments were summarized as follows. Correlation coefficients of serum albumin and thyroxine were ＋0.907 and ＋0.611 in 10$\textperthousand$ and 20$\textperthousand$, respectively. In 30$\textperthousand$ salinity, serum BUN and other 3 kinds of hormones showed all negative correlation coefficients. Correlation coefficients of serum estradiol-17$\beta$ with calcium and cholesterol in 20$\beta$ were ＋0.624, ＋0.733, respectively. Correlation coefficient between serum triglycerides and thyroxine in 30$\beta$ was ＋0.989.

• Journal of Aquaculture
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• v.3 no.1
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• pp.31-37
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• 1990

Ten strains of tilapiine species from genus Oreochromis were cytogenetically studied for genetic stock identification. Both the chromosome numbers(2n=44) were identical in all 10 strains. Heteromorphic sex chromosome pair were not found in any strains. Nuclear volumes vary between O. niloticus(21.0 $\mu$ $m^3$) and O. aureus(22.4 $\mu$ $m^3$)

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2000.05a
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• pp.271-273
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• 2000

Recently, possibility of low protein diet with high energy level for improvement of fish production has been proposed in several fish species, especially under restricted feeding rate, fish responded better on high energy diet than low energy diet McGoogan and Gatlin (1999) stressed another benefit of low protein diet with high energy for fish production, in terms of reduction of nitrogen waste from fish metabolism However, others reported no effect of high lipid in feed on performance of fish (Jover et al. 1999). This was probably because that energy availability o requirement for fish varied based on fish species, protein content or quality in feed, rearing water temperature condition and feeding ration. (omitted)

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.6
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• pp.661-668
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• 2003

Performance of an airlift bioreactor (ABR) containing the immobilized microorganisms was evaluated in an integrated pilot scale recirculating aquaculture system stocked with Nile tilapia (Oreochromis niloticus) at an initial rearing density of $5\%$ and compared to a rotating biological contactor (RBC) for 40 days. The TAN concentration of rearing tank for ABR and RBC were maintained at $0.4\;g/m^3$ and $0.5\;g/m^3,$ respectively, The nitrite nitrogen was completely removed by the ABR. The ABR's aeration was more stable than the RBC's. On the whole, the feasibility of ABR as an aquacultural water treatment unit was recognized.

• Journal of Aquaculture
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• v.1 no.1
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• pp.67-73
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• 1988

A growth experiment of tilapia (offsprings of the hybrid between Oreochromis niloticus and O. mossambicus) under different dissolved oxygen levels in the recirculating water system was conducted at the Fish Culture Experiment Station of the National Fisheries University of Pusan from February 4 to March 5, 1986. Six tanks with a capacity of $1.8m^3$ of water each were used under the same condition of water parameters except for dissolved oxygen levels which were designated to maintain at 1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 mg/$\iota$. Each tank was stocked with 90 kg of fish each averaging 64 to 69 grams. The average water temperature during the course of the experiment was $22.5^{\circ}C$. The results obtained are summarized as follows: The food conversion efficiencies were very good, being 1.05-1.11 at 3.5, 3.0, 2.5 and 2.0 mg/$\iota$ DO levels without any significant differences among them, but at 4.0 mg/$\iota$ the F. C. was 1.39 and at 1.5 mg/$\iota$ it was 1.61 being very poor compared with the others. The daily growth rate performance was best at 3.5 mg/$\iota$ dissolved oxygen level followed by 3.0 and 2.5 mg/$\iota$ with slight differences while at 4.0 and 2.0 mg/$\iota$ DO levels the growths were significantly poor, and at 1.5 mg/$\iota$ DO level it was extremely poor. In 1.5 mg/$\iota$ group, the fish did not accept feed vigorously and after feeding the fish usually concentrated around the inflow point showing oxygen deficiency response. While at 4.0 mg/$\iota$ high feeding rates tended to waste significant amounts of feed while eating and led to water deterioration, and above these levels the results is considered to lead to a waste of energy with uneconomical performance. On the other hand, at and below 2.0 mg/$\iota$ DO level the tilapia certainly showed a poor growth performance. The experiment indicates that the DO range of 2.5$\~$3.5 mg/$\iota$ is the optimum level for the good growth performance.

• Journal of Aquaculture
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• v.9 no.2
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• pp.141-149
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• 1996

Effects of $17{\alpha}$-methyltestosterone ($17{\alpha}-MT$) in rearing water on sex reversal of Nile tilapia (Oreochromis niloticus) were investigated and optimum conditions as initial treatment time, concentrations and treatment durations of hormone were evaluated in this study. For the study of the optimum initial treatment time, 0 to 20-day-old fry were treated by immersion in a 500 ppb solution of $17{\alpha}-MT$. Desirable results were obtained at 12-day-old fish as $86.4\%$ of male induction rates and this frequency was obviously higher than the other age groups. Twelve-day-old fry were immersed in $17{\alpha}-MT$ solutions at concentrations of $0\~2,000$ ppb for 24 hours for the study of dose dependent relationship between sex ratios and concentrations of $17{\alpha}-MT$, Male induction rates of all treated groups were higher than $80\%$, $X^2$ values against the sex ratio of control group indicate that sex reversal has taken place effectively in all experimental groups (P<0.001). Futhermore, 500 ppb treated groups showed highest male incidence of $86.4\%$. Effects of 5 different durations (0, 12, 18, 24 and 30 hours) treated with 1,000 ppb of $17{\alpha}-MT$ were also evaluated. Male induction rate from 0 to 24 hours treated group was increased with treatment durations. However, male incidence of 30-hour treated group ($84.0\%$) was sligthly decreased compare to the 24-hour treated group ($85.2\%$). It is concluded that immersion treatment using $17{\alpha}-MT$ on O. niloticus is possible on sex reversal at low concentration of 500 ppb and short treatment durations within 24 hours with 12-old-day fry.