• 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.

• Korean Journal of Environmental Biology
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• v.38 no.1
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• pp.127-136
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• 2020

This study was conducted to investigate the population characteristics of Nile tilapia (Oreochromis niloticus) in the Daegu Metropolitan City thermal effluent stream (Dalseo Stream) from January to November 2019. The collected fish were identified as 4,247 individuals of 20 species from a total of eight families. The dominant species was O. niloticus with 1,306 individuals and a high relative abundance (30.75%). The water temperature of Dalseo Stream was maintained above 10℃ throughout the year, which means that O. niloticus could inhabit it even in winter. The length-weight analysis showed a regression coefficient b of 3.1496, and a condition factor (k) of 0.0025 with a positive slope. Comparing the water temperature of Dalseo Stream and the total length of O. niloticus per investigation period, the 0-age individuals appeared May 29 when the water temperature was maintained above 22℃. In conclusion, the thermal effluent of Dalseo Stream allowed O. niloticus to survive in winter and maintain stable growth conditions and life cycles. The results of this study will inform ecological information on O. niloticus, which suggests that river management efforts should consider the management of O. niloticus populations for the conservation of fish species diversity.

• Journal of fish pathology
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• v.18 no.3
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• pp.259-268
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• 2005

This study was conducted to know the differences in pathology between artificially induced hemorrhagic anemia (EHA) and hemolytic anemia (ELA) during the anemic and recovery course, using Nile tilapia (Oreochromis niloticus). EHA were induced by repeated bleedings with a volume of about 1% of body weight through caudal vein. ELA were induced by intraperitoneal injections of 1% phenylhydrazine for 2 times. A period of 16 to 49th day was arbitrarily taken as a recovery phase. There were no prominent clinical signs and gross findings except for pale gills during the anemic state of both. Characteristic erythrocytes with a weekly stained cytoplasm started appearing on the 12th day in both and were still noted on the 49 and 20th day respectively in EHA and ELA. EHA and ELA were normocytic hypochromic and macrocytic normochromic in type respectively, although both were normocytic hypochromic during the recovery phase. In liver, fatty degeneration around central vein on the 12-38th day in EHA and hyaline degeneration around central vein on the 12-26th day in ELA were found. In head kidney, increased hemopoiesis was observed on the 12-26th day in EHA and on the 2-12th day in ELA, and macrophages engulfing erythrocytes were observed on the 16-38th day in EHA and on the 2-12th days in ELA. In spleen, activated ellipsoids on the 12-26th day in EHA. and on the 2-20th day in ELA. In ELA, severe accumulation of hemosiderin in both spleen and head kidney were constantly noted from the 2-49th day. On the 49th, Ht was recovered but Hb was still lower than that of control in both anemia.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.4
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• pp.278-283
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• 2002

The response of electrocardiogram(ECG) of Nile tilapia, Oreochromis niloticus [Linnaeus] was studied to the electric stimulus which was given to a certain part of body The experiments were performed in such a way that three levels of electric stimulus (20, 30, 40 Vp ； 10 msec) were given to fishes with electrode inserted into their bodies and then their ECGs were recorded continuously for 60 minutes in the water temperature of 16~18$^{\circ}C$ The results of the experiments were divided by day and night, and then were analyzed by experimental conditions as follows; 1. Nile tilapia reached a stable condition within 3 minutes after the electrode inserted into their bodies during anesthesia. In stable condition, the heart rates average was 45.8 beat/min during daytime and 45.0 beat/min at night. The action potentials average was 1.76 $mutextrm{V}$during daytime and 1.75 $mutextrm{V}$ at night. 2. The heart rates average by three levels of electric stimulus were \circled1 In the stimulus condition, the heart rates were 34.9 beat/min during daytime and 33.4 beat/min at night for the 20 Vp level, 36.8 bea/min during daytime and 36.0 beat/min at night for the 30 Vp level, and 38.0 beat/min during daytime and 36.4 beat/min at night for the 40Vp level. \circled2 In the recovery condition, the action potentials were 45.5 beat/min during daytime an 45.1 beat/min at night for the 20Vp level, 47.9 beat/min during daytime and 49.0 beat/min at night for the 30Vp level, and 51.4 beat/min during daytime and 50.7 beat/min at night for the 40Vp level 3. The action potentials average by three levels of electric stimulus were, \circled1 In the stimulus condition, action potentials were 2.54 $mutextrm{V}$ during daytime and 2.39 $mutextrm{V}$ at night for the 20 Vp level, 3.30 $mutextrm{V}$ during daytime and 2.30 $mutextrm{V}$ at night for the 30 Vp level and 6.05 $mutextrm{V}$ during daytime and 3.23 $mutextrm{V}$ at night for the 40 Vp level. \circled2 In the recovery condition, action potentials were 1.92 $mutextrm{V}$ during daytime and 1.95 $mutextrm{V}$ at night for the 20 Vp level and 2.78 $mutextrm{V}$ during daytime and 2.21 $mutextrm{V}$ at night for the 30Vp level and 3.6 0 $mutextrm{V}$ during daytime and 2.98 $mutextrm{V}$ at night for the 40 Vp level.

• Journal of Aquaculture
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• v.18 no.2
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• pp.122-129
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• 2005

Ammonia is the major limiting factor in intensive aquaculture production systems. Therefore, quantification of ammonia excretion is important for the water quality management in aquaculture systems. Ammonia excretion is known to be affected by many factors such as body weight and dietary protein level (DPL). In this study, experiments were carried out to investigate the effects of body weight and DPLs on the rates of ammonia excretion of Nile tilapia Oreochromis niloticus. Three sizes of fishes (mean initial weight; 4.8 g,42.7 g and 176.8 g) were fed each of two dietary protein levels (30.5% and 35.5%). Daily feeding levels for the three fish sizes of 4.8 g, 42.7 g and 176.8 g were 6%, 3%, and 1.5% body weight per day, respectively. Each group of fish was stocked in a 17.1-L aquarium and all treatments were triplicated. Following feeding, the weight-specific ammonia excretion rate of O. niloticus increased, peaked at 4 to 8 h, and returned to pre-feeding levels within 24 h. Total ammonia nitrogen (TAN) excretion.ate per unit weight decreased with the increase of fish weight for each diet (P<0.05). The TAN excretion rate increased with increasing dietary protein content for each fish size (P<0.05). TAN excretion rates (Y) for each diet with different fish weights were described by the following equations: low DPL diet (30.5%): $Y\;(mg\;kg^{-1}\;d^{-1})=955.69-147.12\;lnX\;(r^2=0.95)$, high DPL diet (35.5%): $Y\;(mg\;kg^{-1}\;d^{-1})=1362.41-209.79\;lnX\;(r^2=0.99)$. Where: X=body weight (g wet wt.). The TAN excretion rates ranged 28.5%-37.1% of the total nitrogen ingested for the low DPL diet (30.5%) and 37.4-38.5% for the high DPL diet (35.5%). Total nitrogen losses of fish fed the high DPL diet $(35.5%;\;0.26\sim0.91g\;kg^{-1}\;d^{-1})$ were higher than those fed the low DPL diet $(30.5%;\;0.22\sim0.68g\;kg^{-1}\;d^{-1})$. The losses decreased per kg of fish as fish size increased. Results will provide valuable information fer water quality management and culture of Nile tilapia in recirculating aquaculture systems.

• Journal of fish pathology
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• v.3 no.2
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• pp.69-77
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• 1990

Tilapia, Oreochromis niloticus, weighing 100g on average was fed on the oxidized pellet diets in peroxide value (POV) 102 meq/kg, with or without the vitamin mixture of C and E for 67 days. After administration of vitamin mixture for 67 days, the fish fed them displayed better growth than the fish fed oxidized pellet only. The fish fed low level of the vitamin mixture or the oxidized pellet retained visceral ceroidosis but did not show myopathy. But the fish administered high level of the vitamin mixture lossed macrophages disposing of ceroid in the viscera. Based on the results, the administration of vitamin mixture at high level was effective as prophylaxis for ceroidosis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.3
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• pp.611-621
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• 2016

This study examined the effects of collagen peptide intake extracted from the tilapia fish (TFCP) on UVB-induced skin in hairless mice. To cause photoaging, the hairless mice were exposed to UVB irradiation three times a week and TFCP was administered with 545 and 1090 mg/kg once a day for 12 weeks. The level of wrinkle formation, thickness of the skin, acute erythema, skin hydration, amount of hydroxyproline, expression of MMPs and filaggrin were measured. Wrinkle formation, thickness of the skin, and acute erythema were significantly lower and skin hydration was higher in the TFCP intake group compared to the UVB-control mice group. In addition, the amount of the collagen and hydroxyproline of the collagen peptide intake group were much higher than the UVB-control group. Oral administration of TFCP inhibited the expression of the MMP-3 and MMP-13 mRNA level as well as activated MMP-2 and MMP-9 induced by UV irradiation, and increased the protein expression of filaggrin in hairless mice skin. In summary, the oral administration of TFCP can inhibit wrinkle formation and protect the skin from UV-damage. Therefore, this study suggests that TFCP is a potential candidate material for skin functional foods.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.1
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• pp.21-26
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• 2002

The behavior of the biological water treatment process on start-up operation was evaluated in the integrated recirculating aquaculture system consisting of a double drain type rearing tank ($2.5 m^3$), a sedimentation tank, a floating bead filter, a foam separator and a rotating biological contactor. A system was stocked with nile tilapia (Oreochromis niloticus) at an initial rearing density of $2\%$ for 2 weeks for acclimated rotating biological contactor. The total ammonia nitrogen (TAN) level increased to $13.6 g/m^3$ on day 4 after adding feed and was decreased to $0.3 g/m^3$ on day 7. The total suspended solid was completely removed during overall experimental period.

• Journal of fish pathology
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• v.25 no.1
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• pp.1-10
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• 2012

It has been reported that various anti-oxidant substances stimulate non-specific immune responses in fishes. In this study it was examined whether N-acetylcysteine (NAC), an anti-oxidant glutathione (GSH) precursor, can modulate non-specific immune parameters in 8 different fishes. NAC was intraperitoneally administered at 10 mg/kg to catfish (Silurus asotus), loach (Misgurnus mizolepis), common carp (Cyprinus carpio), crucian carp (Carassius carassius), eel (Anguilla japonica), snakehead (Channa argus), tilapia (Oreochromis niloticus) and mullet (Mugil cephalus). Forty-eight hours later, chemiluminescence (CL) response of head-kidney leukocytes and serum lysozyme activity were assessed. In all fishes except crusian carp and loach, CL responses were amplified by NAC. Lysozyme activity was increased by NAC in all fish species but not in tilapia. This result suggests that NAC stimulates non-specific immune responses in various species, and that such effects may have beneficial significance in aquaculture for practical utilization.

• Journal of Aquaculture
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• v.8 no.3
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• pp.183-193
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• 1995

Blue tilapia, Oreochromis aureus swim-up fry were fed,0, 1, 10, or 60 ppm $17\alpha-methyltestosterone$(MT) for 30 days (sex reversal period). Fish that had been fed 0 ppm MT during the sex reversal period were subsequently fed 0 ppm MT (0-0), 10 ppm MT (0-10) or 60 ppm MT (0-60) for the next 57 days (post sex reversal period) ; fish that had been fed 60 ppm MT during the sex reversal period were subsequently fed 0 ppm MT (60-0), 10 ppm MT (60-10), or 60 ppm MT (60-60) during the post sex reversal period. One group was fed 1 ppm MT (1-1), while another group was fed 10 ppm MT (10-10) during the entire 87-day experiment. There was a significant inverse relationship between concentration of MT and percentage body protein and percentage body fat at the end of the sex reversal period, while there was a significant positive relationship between concentration of MT and percentage body moisture. MT treatment during the post sex reversal period had greater effects on body composition of males at the end of the post sex reversal period than did MT treatment during the sex reversal period. There was a significant inverse relationship between MT concentrations, during both the sex reversal and post sex reversal periods, and gonosomatic indices (GSI) in males. In females, there was a significant inverse relationship between MT concentrations during the post sex reversal period and GSI.