• Ocean and Polar Research
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• v.38 no.1
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• pp.81-88
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• 2016

In many fish species, including Nile tilapia (Oreochromis niloticus), gonadal development occurs at the expense of stored energy and nutrients. Therefore, reproductive systems are inhibited by limited food supply. It has been well established that reproductive function is highly sensitive to both metabolic status and energy balance. Nothing is known about the possible mediated connection between energy balance and reproduction. Kisspeptin, a neuropeptide product of the Kiss gene has emerged as an essential gatekeeper of reproduction and may be possibly be linked to energy balance and reproduction in non-mammalians. Thus, in this study, the effect of fasting (10 days) on the expression of kisspeptin and the gonadotropin-releasing hormone (GnRH) gene were assessed in Nile tilapia (male and female) using qRT-PCR. In addition, plasma levels of estradiol-$17{\beta}$ ($E_2$) and 11-ketotestosterone (11-KT) in adult tilapia were measured by ELISA. In male tilapia, fasting reduced Kiss2 and GnRH I mRNA expression in the brain and 11-KT level in comparison with the fed tilapia (p < 0.05). In females, however, there were no significant differences in GnRH I mRNA expression and $E_2$ between fish subjected to fasting and those fed (p > 0.05). These data indicate the impact of nutritional states on kisspeptin as a potential regulatory mechanism for the control of reproduction in male Nile tilapia.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.26 no.4
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• pp.380-391
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• 1993

The experimental study was made to propose the treatment method of wastewater in the high-density fish culture system. The BOD to COD ratios of effluents were almost same to 0.65 in the eel-farm, but were various in the farm rearing together with tilapia etc. A BOD rate curve of the eel-farm effluent could be described mathematically by the equation, $BODu=14.1(1-10^{-0.222t})+30.9(1-10^{-0.035(t-8)})$. Nitrification in Biological Fluidized Bed(BFB) system to treat the fish-farm wastewater could be reduce ammonium level up to $65{\sim}79\%$ when ammonium loading rates were between 0.014 and 0.075g $NH_4/g$ BVS-day. Nitrification efficiency was decreased by organic matters in the wastewater when ammonium loading was low(0.014 g $NH_4/g$ BVS-day). T-N removal ratios were decreased to increase loading in denitrification process, because of low C/N ratio. Based on much higher biological mass concentrations, BFB system takes many advantages of a practical viewpoint, such as stability of treatment efficiency and reduction of necessary site area for the facility, as compared with conventional treatment systems.

• Journal of Aquaculture
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• v.4 no.1
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• pp.1-12
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• 1991

A series of rearing experiments were conducted to determine the growth rates and feed conversion efficiencies of tilapia in accordance with body size or age in nearly total closed system glass aquariums ($270\;\ell$ each in water volume) and concrete tanks ($4000\;\ell$) from April 10 to October 16, 1987. The fish used for the experiments was a Japanese strain of Oreochromis niloticus, and the size of the fish ranged from 7 g to more than 1,000 g in body weight. The starting stocking rates for each experimental lot were 10 to 20 kg in the glass aquarium ($3.7{\%}$ to $7.4{\%}$ of water volume) and 200 kg in the concrete tank ($5{\%}$ of water volume). A single experimental rearing term was 14 days with slight variations on occasions. Water temperature was designed to be kept at $26^{\circ}C$ but slight fluctuations were inevitable. Dissolved oxygen level was designed to be maintained at around $3\;mg/\ell$, but it also showed some variations. The ammonia level in the glass aquarium section once reached up to $18\;mg/\ell$, but generally remained at around $4\;mg/\ell$, and in the concrete tank section it was maintained at around $1\;mg/ell$. The feed was composed of mainly soybean meal with a small amount of fish meal as the protein source, and the crude protein content was about $32{\%}$. Mean daily growth rate was $3.5{\%}$ of body weight with 0.9 in food conversion ratio in the glass aquarium when the mean weight of fish was around 10 g with gradually reduced performances as the fish grew bigger. When the mean weight was 800 g, mean daily growth rate was $0.5{\%}$ with about 1.5 in food coversion for fish in the glass aquarium, and $0.8{\%}$ and 1.6 for fish in the concrete tank, respectively. According to the mean growth rate obtained from this experiment, it was calculated that the fish reared in the concrete tank require 223 days from 50 g to reach 1,000 g which is the ideal size for market in Korea, at the conditions provided as above, and 302 days from 10 g fingerlings to 800 g fish in the glass aquarium conditions of the closed recirculating water system.

• Journal of Aquaculture
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• v.8 no.4
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• pp.295-306
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• 1995

The present study was performed to produce supermales and superfemales in Oreochromis niloticus by combination of induced sex reversal and diploid gynogenesis. More than $95\%$ of female was obtained by oral administration of $17\beta-estradiol$ (480 mg/kg diet) to the eutheroembryonic larvae of this species. The result of progeny tests with XY pseudofemales showed that incidences of male progeny were ranged from $71.4\%\;to\;73.7\%$. p.opo.lion of male from XY pseudofemale was not significantly different (P>0.05) from that of $\chi^2$ (1:3), but it was significantly different (P<0.01) from that of $\chi^2$(1:1) Gynogenetic diploids were produced by applying cold shocks 3 min after insemination to the eggs of XY pseudofemale sperms were genetically inactivated by ultraviolet rays of 4,050 $erg/mm^2$. Fertilization rates of gynogenetic diploids were not different from that of their controls, however, hatching rates and early survival rates were silghtly lower than those of controls. In the cytogenetic studies, there was no difference in the size of cell and nucleus between the gynogenetic diploids and the controls. At 80 days after hatching, frequencies of gynogenetic male were higher than those of gynogenetic female (P<0.01) in their population.

• 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 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.

• Journal of fish pathology
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• v.32 no.2
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• pp.105-111
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• 2019

Citurs unshiu Markovich is a medicinal product of dried tangerine peel (DTP). It is effective on antioxidation, and getting fame as a medicine and functional food. By utilizing DTP as a feed additive, we aim to enhance the growth rate, innate immunity, and bacterial infection resistance to Tilapia. The DTP extract was added to the feed weight by 0.1, 0.5, 1, 5% and then fed to tilapia for 7 days to evaluate the innate immunity parameter, growth rate and anti-bacterial activity. Innate immunity parameter results showed that the ROI was significantly higher in the 5% group added at high concentration, while showing decrease or no differences in other experimental groups. In other parameters, all the experimental groups showed no significant difference or decreased compared to the control group. The challenge test showed a high survival rate of 71% in the 0.5% group and the lowest in the control group (36%). For the growth rate, the feed efficiency was improved in all groups except for the 0.1% group compared to the control group. In conclusion, DTP extract has bacterial resistant effect in while not affecting innate immune system of fish. Also, it has shown the potential as a possible feed additive as it has brought the improvement on feed efficiency ratio.

• Journal of fish pathology
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• v.24 no.3
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• pp.247-254
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• 2011

The purpose of this study was to obtain reference data of parameters for hematological health diagnosis in cultured freshwater fish and also evaluate application of automatic dry-type chemistry analyzer (FUJI DRI-CHEM 3000) used to those blood tests. A blood profile of total 200 fish for rainbow trout (Onchorhynchus mykiss), israel carp (Cyprinus carpio), tilapia (Oreochromis niloticus) and eel (Anguilla japonica) cultured in Inland Fisheries Research Institute of NFRDI was determined by hemoglobin (Hb) and plasma chemistry tests: total protein (TP), albumin (ALB), alkaline phosphatase (ALP), blood urea nitrogen (BUN), lactate dehydrogenase (LDH), triglyceride (TG), total cholesterol (TCHO), creatinine (CRE), aspartate aminotransferase (AST), alanine aminotransferase (ALT), glucose (GLU). The values of ALT, TG, LDH, ALB, TCHO, AST and ALP were outside from the minimum and/or maximum of the established detectable range of the analyzer. ALT and TG were not detectable in the range of 67%~61.5%. LDH, ALB and TCHO were not detectable in the range of 36~17%. AST and ALP were not detectable in the range of 5.5~0.5%. However, the values of BUN, CRE, GLU, Hb and TP were below the detectable limits of the analyzer.

• 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.42 no.5
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• pp.426-433
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• 2009

Fish scales have potential in functional food preparation due to their antioxidant and antihypertensive properties. We investigated the angiotensin I converting enzyme (ACE) inhibitory activity of Tilapia mossambica scale extracts. Hydrolysates of tilapia scales were prepared by enzymatic extraction using five proteases (${\alpha}$-chymotrypsin, Alcalase, Kojizyme, Protamex and trypsin) after scales were treated with hot water for 3 hr. Scale enzymatic hydrolysates prepared using both hot water and enzyme treatments exhibited elevated hydrolysis (about 25%-55%) compared to only enzyme treatment (about 15%-45%). Enzymatic hydrolysates (1 mg/mL) prepared by both hot water and enzyme treatments also showed significantly increased ACE inhibitory activities from about 20%-75%. The pattern of ACE inhibitory activities was similar to the degree of hydrolysis. Alcalase and ${\alpha}$-chymotrypsin hydrolysates displayed the highest ACE inhibitory activities ($IC_{50}$ = 0.83 mg/mL and 0.68 mg/mL, respectively). In addition, the ACE inhibitory effects of $IC_{50}$-chymotrypsin hydrolysates increased with decreasing molecular weight (5 kDa>, 10 kDa> and 30 kDa>), with the 5 kDa> fraction displaying the highest ACE inhibitory activity (about 89.9% and $IC_{50}$ = 0.1 mg/mL). We suggest that the peptide compounds of enzymatic hydrolysates prepared from tilapia scale enhances ACE inhibitory activity and might be useful as an antihypertensive material.