• Korean Journal of Food Science and Technology
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• v.25 no.2
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• pp.185-190
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• 1993

Tilapia cultured in fresh water were acclimated in sea water with daily increase of $5%_{\circ}$ of salinity and it was completely terminated at the 7th day (0 week). Each three tilapia acclimated were examined weekly based from 0 week to elucidate changes of chloride cells in gill, mineral contents and physical properties in muscle and biochemical characteristics in myofibrils. Chloride cells existed in gills were gradually developed in number and size by acclimation to sea water and became to almost constant state at the third week. Shearing value, compressing strength and content of minerals such as Mg, Na and K in muscle were showed remarkable increase by acclimation to sea water in comparison to those of muscle from tilapia reared in fresh water. Myofibrillar $Mg^{2+}-,\;Ca^{2+}-$ and $K^+(EDTA)-ATPase$ activities of tilapia acclimated in sea water also increased showing significant statistic difference (p<0.01) from those of tilapia reared in fresh water However. thermostability of myofibrils was dropped by acclimation to sea water. The increase of shearing value and compressing strength in the muscle of tilapia by acclimation to sea water would be attributed to the increase of myofibrillar ATPase activities which act to accelerate the decomposition rate of ATP. Therefore, it is suggested that this phenomenon associated with muscle contraction could be brought an improvement of texture of tilapia acclimated in sea water.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.15 no.1
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• pp.47-51
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• 1982

Red tilapia fingerlings were tested for 45 days on the growth rate in a closed recirculating water system omitting filter bed and was compared with common carp fingerlings grown together in the same tank and also with red tilapia fingerlings grown in a well conditioned conventional pond. The tank water was kept in deepgreen colour by heavy phytoplankton bloom during the most of the experimental period and duckweeds, Lemna sp. and water hyacinth, Eichhornia crassipes were put to grow in the parts of the water system. Total ammonia level in the tank was mostly kept at about 5 to 7 ppm, with a fluctuation between 3.4 and 11.2 ppm. Average daily growth rate of the tilapia in the experimental tank was $6.5112\%$ without any mortality, compared to $3.617\%$ for common carp fingerlings involving some mortality in the same tank, and to $5.7712\%$ for the tilapia grown in the conventional pond. The feed used for the experiment was one prepared for the rearing of common carp, and the duckweed grown in parts of the water system was routinely collected and fed to the tilapia in the tank as supplementary diet probably satisfying unknown growth factors.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.6
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• pp.675-678
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• 2012

The study examined the effect of levamisole on the natural cytotoxic cell (NCC) activity of Nile tilapia (Oreochromis niloticus) head kidney (HK) leukocytes. In vitro, HK leukocytes were incubated with $10^{-4}$ to $10^4$ ng of levamisole/ml for 5, 20 or 40 h and then their NCC activity against target cells was assayed. The NCC activity appeared to increase after a 20 h of incubation. In vivo, tilapia were fed commercial diet containing 0, 50, 100 or 300 mg of levamisole/kg for 12 consecutive days. Then, the fish were fed a commercial normal diet and samples harvested weekly 0 to 8 weeks after levamisole administration. The NCC activity was augmented uniformly at all times examined until the end of the experiment. In conclusion, levamisole effectively enhanced and maintained tilapia NCC activity.

• Fisheries and Aquatic Sciences
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• v.13 no.4
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• pp.343-349
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• 2010

The effects of osmotic stress on the non-specific immune response of Nile tilapia, Oreochromis niloticus, were investigated. Osmoregulatory mechanism of tilapia has been studied, but less information is available about innate immune response of O. niloticus faced with hyperosmolality. Acute osmotic stress was elicited by transferring tilapia from freshwater (FW) to 24 psu seawater (SW). Non-specific immune parameters including lysozyme activities of plasma and head kidney (HK), alternative complement pathway (ACP) activity in plasma, phagocytic capacities of spleen and HK immune cells, and respiratory burst activity of immune cells in both HK and spleen were analyzed. Lysozyme activities were increased at 1 h and 30 h after transfer to SW, but decreased at 10 h after SW transfer. Conversely, ACP activity increased 10 h after SW transfer. Phagocytic capacity increased slightly at 1 h and 5 h after SW transfer, and respiratory burst activity showed an increase in superoxide release at 10 h after SW transfer. Taken together, these results indicate that the exposure of tilapia to hyperosmotic conditions has immunostimulatory effects on cellular and humoral immune reactions.

• Fisheries and Aquatic Sciences
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• v.26 no.4
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• pp.282-293
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• 2023

Nile perch and Nile tilapia are major commercial species in Uganda, and thus require continuous production. However, their production is impacted by anthropogenic activities such as fishing in breeding habitats. The aim of this study was to identify and characterize Nile perch and Nile tilapia fish breeding habitats on Lake Kyoga. Water quality, lake bottom, fish and vegetation type samples were collected from 20 sites in April of 2021 and 2022. Key informant interviews were conducted with experienced fishermen at five fish landing sites. The water quality parameters indicated significant difference within the sites using analysis of variance. Sandy and muddy bottom types were equally spread at 40% each by use of a pie chart. Fish gonads showed no significant difference among the 20 sites. Bivariate correlation analysis of the vegetation types indicated a strong negative correlation with Nile perch while Nile tilapia had a positive correlation. Principal component analysis of the water quality, fish gonads and habitat vegetation components cumulatively contributed 82.5% in characterizing a fish breeding habitat. Four sites for Nile perch and four sites for Nile tilapia were characterized as breeding sites on Lake Kyoga and are recommended for mapping and gazettement as breeding habitats for sustainable fisheries management.

• Journal of fish pathology
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• v.19 no.3
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• pp.285-288
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• 2006

The respiratory burst activity of tilapia (Oreochromis mosambicus) phagocytes agaisnt Edwardsiella tarda ghosts produced by gene E mediated lysis was investigated. Stimulation with E. tarda ghosts (ETG) showed markedly higher respiratory burst activity than that with formalin killed E. tarda (FKC) in phagocytes. This result may suggest that ETG can induce effective cellular immune responses in fish.

• Development and Reproduction
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• v.14 no.1
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• pp.21-25
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• 2010

Nile tilapia (Oreochromis niloticus) are mouth-brooders so that the females holding eggs in their mouth sacrifice their somatic growth for reproduction. For this reason, artificial control of reproduction for the culture of this species has been of interest. Manipulation of photoperiod is an emerging technique for such purpose, but little information is available to establish appropriate photoperiod regime. To obtain necessary basic information, sexually mature females were individually accommodated to glass aquarium, and the spawning activity of these females were monitored for two years under natural photoperiod regime. Female tilapia spawned most frequently on March, April and May when the day length gradually increased from 11 hours to 14 hours and least frequently on September, October, November and December when the day length gradually decreased from 13 hours to less than 10 hours in the first year. The decrease of spawning frequency as day length decreased was also observed in the second year, although the increase of spawning frequency as day length increased was less clear. Spawning of female tilapia was less active when the night was dark due to the disappearance of moonlight (Dark Phase), compared to the Phase of Getting Lighter, Light Phase and Phase of Getting Darker. Results from this study suggest that long day length, particularly increasing phase, is favoured for active spawning of Nile tilapia, and that this species, as a tropical fish species, may utilize changing lunar phases as a secondary environmental cue for reproduction.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.6
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• pp.648-653
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• 2012

The present study examined the effects of dietary supplementation with nucleotide (inosine monophosphate product, IMP) on the growth performance, feed utilization, and non-specific immune responses of juvenile tilapia Oreochromis niloticus. Triplicate groups of tilapia (initial body weight, $7.4{\pm}0.04$ g) were fed experimental diets containing 0%, 0.05%, 0.1%, and 0.2% IMP. Fish were fed six times a day until apparent satiation for 13 weeks. At the end of the feeding trial, final body weight and food utilization of fish fed 0.1% IMP were significantly higher than those of fish fed the control diet. Results of hematological parameters were not affected by dietary IMP. However, blood protein level was significantly higher in the 0.05% treatment, as compared to that of the control and 0.2% IMP diets. Myeloperoxidase activity was higher in fish fed 0.1% IMP than in fish fed the control and 0.2% IMP diets. These results suggest that dietary supplementation with IMP can enhance the growth performance, feed utilization, and innate immune response of juvenile tilapia. The optimal IMP supplementation level appears to be 0.1% in practical feed formulations for tilapia.

• Journal of Animal Science and Technology
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• v.56 no.1
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• pp.3.1-3.7
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• 2014

We examined the effects of Prunella vulgaris Labiatae (P. vulgaris L.) on specific and non-specific immune responses of Nile tilapia, Oreochromis niloticus. The optimal concentration without toxicity of P. vulgaris was determined to $30-40{\mu}g/ml$ in vitro and $120{\mu}g$/100 g of fish in vivo. P. vulgaris significantly elicited an antibody titer compared to FCA or ${\beta}$-glucan. ${\beta}$-glucan plus P. vulgaris group synergistically enhanced antibody production. No significant difference in antibody production was observed between P. vulgaris and P. vulgaris plus ${\beta}$-glucan group. A respiratory burst activity of head kidney (HK) leucocytes of tilapia administered with 300 or $500{\mu}g$ P. vulgaris was significantly (p < 0.05) enhanced compared with the PBS-injected control group and FCA-treated group. Maximum increase in the NBT reduction value was observed in $500{\mu}g$ P. vulgaris group but no significant difference was found between 300 and $500{\mu}g$ P. vulgaris group. The level of serum lysozyme activity was significantly (p < 0.05) higher in the 300 and $500{\mu}g$ P. vulgaris than $100{\mu}g$ P. vulgaris and FCA group. The phagocytic activities of HK leucocytes from tilapia administered with 300 and $500{\mu}g$ P. vulgaris were significantly (p < 0.05) higher than $100{\mu}g$ P. vulgaris and the control group. P. vulgaris was revealed with a good immunoadjuvant evoking the specific and non-specific immune responses of tilapia.

• Animal cells and systems
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• v.4 no.3
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• pp.299-304
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• 2000

In the present paper, the immunostimulatory effects of the extracellular products (ECP) from Mycobacterium spp. and various adjuvants on the non-specific immune responses of Nile tilapia, Oreochromis nilotica, were examined. Nile tilapia were immunized by injecting ECP of Mycobacterium spp. (strain TB40, TB267 or the type strain Mycobacterium marinum) into their swim bladders. A variety of adjuvants like as Freund s complete adjuvant (FCA), Freund's incomplete adjuvant (FIA) and Titremax were similarly injected into additional groups of tilapia. The number of nitroblue tetrazolium (NBT)-positive cells observed in the swim bladder of the immunized fish was signigicantly increased by the fourth day post-immunization. By day 8, the numbers of NBT-positive cells were fewer in fish immunized with ECP from mycobacteria strains TB40 or TB267 than those immunized with ECP from M. marinum or fish injected with FCA or FIA. The level of Iysozyme activity detected in the serum of fish 40 alter immunization with ECP from various Mycobacterium spp. was also significantly higher than that found in the serum of the control fish. Head kidney macrophages showed enhanced reduction of NBT when cultured in vitro with 1 $\mu$ g/ml of ECP. Concentrations greater than this (10 or 100 $\mu$g/ml) were found to suppress the reduction of NBT by the macrophages. ECP from Mycobacterium spp. and the various adjuvants used in the study all appear to be good activators of the non-specific immune responses of Nile tilapia.