• Fisheries and Aquatic Sciences
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• v.15 no.4
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• pp.305-311
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• 2012

We investigated compensatory growth of Nile Tilapia Oreochromis niloticus in structural size and live weight in response to different deprivation periods and refeeding. Four treatments were assigned randomly to fish in 12 glass tanks, with each treatment performed in triplicate. The control group was fed to satiation three times a day throughout the experiment. The other three treatment groups were starved for 1 week (S1), 2 weeks (S2), or 4 weeks (S4) and then fed until the end of the experiment. After the experiment, no significant differences were observed among S1, S2, and the control group in average weight or length, whereas the weight and length of S4 were significantly reduced. Relative condition factors of the three starved groups decreased significantly until the end of the restricted period but recovered rapidly after refeeding. The specific growth rate in weight ($SGR_W$) of the three restricted groups recovered quickly upon refeeding and were significantly higher than the control group, but these differences disappeared gradually until the end of the experiment. No significant difference in specific growth rate in length ($SGR_L$) was noted between the control group and the three restricted groups after refeeding. All three groups showed hyperphagia for a short period upon refeeding, and no statistical differences were observed in feeding efficiency among the four groups.

• Journal of Aquaculture
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• v.15 no.2
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• pp.119-121
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• 2002

A study on the acute toxicity in the Nile tilapia, Oreochromis niloticus fry showed that the 24hr-$LC_{50}$ was 18.6% for NaCl,152 ppm for formaline and 2.1 ppm for $KMnO_4$. The fry responded to narrow range of concentration of all the tested chemicals and their toxic effects were dose-dependent.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.1
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• pp.51-56
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• 2001

Changes of gill tissue and body composition of grey mullet (Mugil cephalus) and Nile tilapia (Oreochromis niloticus) by the manipulation of salinity were observed in a recirculating rearing system. Salinity was increased from $0\%_{\circ}$ to $33\%_{\circ}$for 1 day and remained far 15days, thereafter salinity was decreased from $33\%_{\circ}$ to $0\%_{\circ{$ for 1 day and remained for other 15 days. Any morphological differences of gill lamella in grey mullet were not observed in seawater and freshwater. However, on day 2 in exposure to seawater, Nile tilapia showed the edema and bloodclot in gill lamella. In the case of grey mullet, mitochondria and tubular system of chloride cell were more densely packed according to the salinity increase. The whole body of grey mullet showed no significant differences in moisture content during experimental period. However, moisture content in whole body of the Nile tilapia was signincantly decreased when exposed to seawater. Protein content in whole body of grey mullet showed no significant difference between beginning and day 15 of the experiment.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.2
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• pp.144-148
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• 1999

This study was conducted to test actual oxygen consumption rates of Nile tilapia (Oreochromis niloticus) at a commercial scale high density culture tank in the recirculating culture system, with a special emphasis on the oxygen consumption rate of this species with different daily feeding frequencies. Nile tilapia, an average of 400 g and a total wright of 390 kg, were stocked in a circular concrete tank of 2.9 m in diameter and 0.8 m in depth, in a recirculating culture system. The fish were fed commercial diet 1, 2, 5, and 9 times per day between 09:00 h and 19:00 h. feed was evenly supplied where the fish were fed more than once a day. Dissolved oxygen of influent and effluent water was monitored every 50 seconds by a computer with electrodes for 24 hours. The standard metabolic rate of tilapia was $39.31{\pm}4.4mg\;O_2/kg$ fish/hr in the present study. The maximum oxygen consumption was reached between 30 to 50 minutes after feeding. The maximum oxygen consumption levels of 1, 2, 5, and 9 feeding times per day were 161.2, 123.4, 111.1 and 111.1 mg $O_2/kg$ fish/hr, respectively. While the mean oxygen consumption levels of 1, 2, 5, and 9 feeding times per day were $79.9{\pm}21.5,\;81.3{\pm}14.8,\;84.2{\pm}9,9$ and $98,9{\pm}11.0mg\;O_2/kg$ fish/hr, respectively. These results show that oxygen consumption rates are not much different between the feeding frequencies. These results could be used to design to provide desirable oxygen supply system in the recirculating high-density tilapia culture system.

• Journal of Animal Science and Technology
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• v.53 no.6
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• pp.563-569
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• 2011

The effects of cortisol on proliferation and apoptosis of tilapia surface immunoglobulin positive ($sIg^+$) lymphocytes isolated from different tissues were investigated. $sIg^+$ lymphocytes from the tilapia head kidney (HK) and spleen showed a higher proliferation and lower intracellular calcium ($Ca^{2+}{_i}$) level to Ig-crosslinking compared with peripheral blood $sIg^+$ lymphocytes. Peripheral blood $sIg^+$ lymphocytes stimulated with lipopolysaccharide (LPS) showed high levels of apoptosis in the presence of cortisol. HK and to a lesser extent spleen $sIg^+$ lymphocytes, although less sensitive than their equivalent in peripheral blood, showed cortisol-induced apoptosis irrespective of LPS stimulation of control levels. Compared to plasma values measured during stress conditions, proliferation regardless of LPS stimulation was apparently suppressed by cortisol that is effective in inducing a significant increase in apoptosis in all three different cell populations of $sIg^+$ cells, suggesting the immunoregulatory effect of cortisol in both LPS stimulated and non-stimulated conditions. Different sensitivity of $sIg^+$ cells to the cortisol, in regard to developmental stage and activity, could be related in inhibiting excessive and continuing depletion of $sIg^+$ lymphocytes.

• Molecules and Cells
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• v.23 no.3
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• pp.331-339
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• 2007

It has been suggested that the structure and function of nuclear receptors are evolutionally conserved. Here, we compare the molecular functions of the nile tilapia (Oreochromis niloticus) small heterodimer partner (nSHP/NR0B2) and the Dosage-sensitive sex reversal AHC critical region on X chromosome gene 1 (nDAX-1/NR0B1) with those of human SHP and DAX-1 (hSHP and hDAX-1, respectively). We found that, upon transient cotransfection of human cells, nDAX-1 repressed the activity of tilapia SF-1 (nSF-1) but not that of human SF-1, although the physical interaction with human SF-1 was retained. Similarly, nSHP repressed the activity of nSF-1, whereas hSHP did not, pointing to divergent evolution of SHP/SF-1 in fish and human. We thus propose that the repressive functions of SHP and DAX-1 have been conserved in fish and mammals although with different transcriptional targets and mechanisms. These differences provide new insights into the physiological diversification of atypical orphan nuclear receptors during vertebrate evolution.

• Animal cells and systems
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• v.4 no.4
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• pp.341-345
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• 2000

It has been very difficult to develop and evaluate efficient fish vaccines because fish immune cells have not been properly characterized. In this study, we investigated the cell-mediated immunological properties of B- and T-like cells in Nile tilapia (Oreochromis nilotica). Surface immunoglobulin negative ($slg^{-}$) cell population proliferated in response to mammalian T-cell mitogens PHA and Con A, while surface immunoglobulin positive ($slg^{+}$) cells responded to the B-cell mitogen LPS. The slg$^{[-10]}$ cells from hemocyanin (HC)-immunized Tilapia, compared to the non-immunized control, reacted more to PHA than to Con A. Unexpectedly, antigen (Ag)-specific response was observed in both $slg^{-}$ and $slg^{-}$cells. Regardless of HC immunization, whole leukocytes from 8 head kidney of fish showed natural killer (NK)cell activity. Especially, NK cell activity was much higher in slg$^{[-10]}$ cells than in slg$^{+}$cells, indicating the possibility that fish NK cells were not at least associated with slg$^{+}$ cell population and not activated by Ag. Further understanding of functional fish immune cells will help to evaluate and develop effective vaccines for fishes and to monitor the course of therapy In infected fishes.hes.

• Fisheries and Aquatic Sciences
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• v.20 no.11
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• pp.30.1-30.10
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• 2017

Small-scale fish farmers in developing countries are faced with challenges owing to their limited information on aquaculture management. Nile tilapia farmers in Teso North Sub-County recorded lower yields than expected in 2009 despite having been provided with required inputs. Water quality was suspected to be the key factor responsible for the low yields. This study sought to assess the effects of earthen pond water physico-chemical parameters on the growth of Nile tilapia in six earthen fish ponds under semi-intensive culture system in Teso North Sub-County. The study was longitudinal in nature with pond water and fish being the units of analysis. Systematic sampling was used to select five ponds while a control pond was purposively selected based on its previously high harvest. Four ponds were fed by surface flow and two by underground water. Each pond was fertilized and stocked with 900 fry of averagely 1.4 g and 4.4 cm. Physico-chemical parameters were measured in-situ using a multi-parameter probe. Sixty fish samples were randomly obtained from each pond fortnightly for four months using a 10 mm mesh size and measured, weighed and returned into the pond. Mean range of physico-chemical parameters were: dissolved oxygen (DO) 4.86-10.53 mg/l, temperature $24-26^{\circ}C$, pH 6.1-8.3, conductivity $35-87{\mu}S/cm$ and ammonia 0.01-0.3 mg/l. Temperature (p = 0.012) and conductivity (p = 0.0001) levels varied significantly between ponds. Overall Specific Growth Rate ranged between 1.8% (0.1692 g/day) and 3.8% (1.9 g/day). Ammonia, DO and pH in the ponds were within the optimal levels for growth of tilapia, while temperature and conductivity were below optimal levels. As temperature and DO increased, growth rate of tilapia increased. However, increase in conductivity, pH and ammonia decreased fish growth rate. Temperature and DO ranging between 27 and $30^{\circ}C$ and 5-23 mg/l, respectively, and SGR of 3.8%/day and above are recommended for higher productivity.

• Journal of Aquaculture
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• v.5 no.2
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• pp.157-165
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• 1992

Experiments were conducted to find out suitable dietary lipids in the practical feed for Nile tilapia, Oreochromis nilotius. Soybean oil, corn oil, fish oil or cuttlefish liver oil was mixed in the diet and tested. The best weight gain and feed efficiency were obtained from the fish fed soybean oil or corn oil, both rich in 18 : 2n-6. But the growth rate of fish fed diet with fish oil or cuttlefish liver oil were inferior. The levels of 20 : 3n-9 in the total lipid were not different in all tested lipids, but that in the polar lipid of the fish oil or cuttlefish liver oil were lower than that in the soybean oil or corn oil. Thus, vegetable oil such as soybean oil or corn oil, rich in 18 : 2 n-6, were suitable as dietary lipid for Nile tilapia. Unlike other fish species, fish oil or cuttlefish liver oil showed no essential dietary value for this species.

• Journal of Aquaculture
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• v.10 no.3
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• pp.373-380
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• 1997

The experiments were conducted to improve the mass production of Nile tilapia, Oreochromis niloticus, seed in closed recirculation systems. It was observed that smaller females (340g av. body weight) under lower stocking density (1.2 kg/$m^2$)) group produced 3.6 times more fry than larger females (612g av. body weight) under higher stocking density (2.1kg/$m^2$) group when the fry were collected at 30 days after the broods stocked. The clutch removal method where the eggs and sacfry were collected from female mouth followed by artificial incubation showed improved seed production, when compared to the traditional natural mouth-brooding method by harvesting free swimming fry from brood tanks (P<0.05). Under the clutch removal method, short-term incubatin of brooders (14 days) was proven to be more effective than long-term incubatin (21 days). Hatching success of clutch removed eggs was ranged from 55.7 to 91.5% in 1.8$\ell$ of upwelling incubators depending on the different development stages.