Male Monosex Research Articles

Formation of Male Sex Tilapia Larvae (Oreochromis niloticus) Using Natural Methyltestosterone Hormone

Aims: Obtaining a productive tilapia, by changing the sex of the tilapia larvae into male monosex. This was achieved by determining the effect of the duration of administrating the natural methyltestosterone (MT) hormone on the male sex of tilapia using the Immersion method.
 Methodology: The study was conducted at the Northern Region Marine and Fisheries Service Branch, Wanayasa Freshwater Fish Seed Development Center, Purwakarta Regency, West Java Province, Indonesia. The experimental design used a completely randomized design (CRD) with 5 treatments and 3 replications. The study used the Immersion method where untreated tilapia and the four hormones tilapia. The treatments are as follows:
 A = untreated tilapia
 B = tilapia treated in 17a-MT (5h-100mg/L)
 C = tilapia treated in MT (5h-350mg/L)
 D = tilapia treated in MT (10h-350mg/L)
 E = tilapia treated in MT (15h-350mg/L)
 Results: Tilapia larvae used were aged 6 days after hatching and reared for 40 days, then the male and SR sex were observed. The results of this study showed that the duration of immersion of tilapia larvae using natural MT significantly affected the male tilapia which resulted in the highest male percentage at 15 h of immersion of 80.2%, then followed by 10-h immersion of 75.6% with the same SR value of about 90%.
 Conclusion: Administration of natural MT using cow testis meal by immersion method at different durations significantly affects male sexual development in 6-day-old tilapia larvae. Based on the obtained data analyses, the percentage of male tilapia in the 40-day experimental study shows the most effective duration in treatment E (15 h) with a measure of 350 mg/l, which is 80.2%. Further studies regarding the relationship between sex change and the growth of sex-changed fish as an effect of immersion duration.

Effect of Stocking Density and Feeding Strategy on Zootechnical Parameters and Profitability of Nile Tilapia (Oreochromis niloticus) Reared in Floating Cages in Toho-Todougba Complex Lagoon in Benin Republic

This study aimed to compare the growth performance and economic profitability of rearing Oreochromis niloticus in floating cages using three feeding strategies (5 days a week, 6 days a week, and 7 days a week) coupled with three stocking densities (20, 40, and 60 fish·m−3). Male monosex fish measuring 6.44 ± 0.18 cm and weighing 3.42 ± 0.7 g were used. The controls were weighed every 15 days from the 35th day of rearing until 185 days to assess zootechnical parameters. BioMar feed (Efico Cromis 832F) was used during the study, and the feed ration was adjusted for each treatment every 2 weeks. At the end of the study, the average weights varied from 293.09 g to 468.41 g for the conditions of 40 fish·m−3 with a 5/7-day diet and 20 fish·m−3 with a 7/7-day diet, respectively. The yield per m2 values were between 7.11 kg and 23.17 kg, respectively. On the other hand, the economic profitability was better with the condition of 40 fish.m−3 with daily feeding. These results suggest that in the Toho-Todougba lagoon complex, a stocking density between 40 and 60 fish·m−3 coupled with daily feeding (three times a day) promotes the optimization of fish production and profitability of fish farming.

Comparative study on growth performance and survival of Indian major carps and male monosex tilapia in recirculating aquaculture system

An experiment was performed in a recirculatory aquaculture system (RAS) to carry out a comparative study on the growth performance and survival of Indian major carps (Labeo rohita and Gibelion catla) and monosex tilapia (Oreochromis niloticus) fingerlings for a period of 90 days. Ten fingerlings each of L. rohita (average weight 30±0.1 g), G. catla(average weight 28±0.1 g) and O. niloticus (average weight 31.5±0.2 g) were distributed randomly into twelve cages, in quadruplicates. L. rohita and G. catla were fed commercial floating feed (30% crude protein and 5% crude lipid) ad libitum while O. niloticus were initially fed at 3% of the body weight upto 100 g size and was changed to 2% of the body weight. There was significant (p<0.05) increase of daily weight gain, percentage weight gain and specific growth rate (SGR) in O. niloticus followed by L. rohita and G. catla. Significantly lower (p<0.05) feed conversion ratio (FCR) and higher (p<0.05) protein efficiency ratio (PER), protein productive value (PPV) and lipid productive value (LPV) were found in O. niloticus followed by L. rohita and G. catla. At the end of the experiment, survival was similar for all three fish species, however total biomass was significantly (p<0.05) higher in O. niloticus followed by L. rohita and G. catla. The findings of this study showed the potential of RAS as an alternative to the pond culture of monosex tilapia and rohu.Keywords: Growth performance, Indian major carps, Monosex tilapia, Survival, Recirculatory aquaculture system

Effect of elevated fry rearing temperature on survival rate, growth performance, and sex ratio of three Oreochromis niloticus populations of Ethiopian Rift Valley Lakes

Sex-reversal in Oreochromis niloticus is used to produce mono-sex males which are desired in aquaculture for better growth performances and population control. The present study was aimed at studying the effect of elevated fry rearing temperature on survival, sex ratios, and growth performances of O. niloticus populations of Lakes Chamo, Koka, and Ziway. Fries from five separate brood pairs of each population were either treated (T) in elevated fry rearing temperature of 36 ± 1°C or kept at room temperature of 24 ± 1°C as control (C) groups for 10 days (phase-I) and then grown in outdoor ponds for six months (phase-II). Survival rates in T groups (74.0 to 91.7%) were lower than that of C groups (83.3 to 97.0%) in all the three populations in phase-I but not in phase-II. Chamo population was better in survival rate (88.4% and 95.4% in Phase-I, and 95.4% and 95.3% in phase-II) than Koka population (85.8% and 91.3% in Phase-I, and 93.9% and 93.5% in phase-II) and Ziway population (80.2% and 88.6% in Phase-I and 90.2% and 91.9% in phase-II) both in T and C groups respectively. The Chamo population also attained significantly (p<0.05) higher mean final weight of 31.58 ± 6.78 g and 24.26 ± 6.67 g in T and C groups respectively, followed by that of Koka population with 21.70 ± 5.10 g and 18.83 ± 4.16 g while Ziway population with mean final weight of 17.49 ± 4.60 g and 16.81 ± 4.15 g was the least both in T and C groups. The overall sex ratios in T groups were skewed towards male but balanced in all C groups of each population. Better growth was achieved only in T groups with higher male ratio than their corresponding C groups. The number of sensitive brooding pairs and the overall male ratio in T groups were higher in the Koka population (40%, 61.68%) than in Ziway (20%, 56.78%) and Chamo (20%, 56.39%) populations respectively. However, the sensitivity of sex reversal to elevated fry rearing temperature was wide between individuals within each population than across the three populations. Hence, sensitive individuals can be selected from the populations and their degree of sensitivity can be improved through continuous selection of progenies from temperature-sensitive parents.

Optimization of 17α-methyltestosterone dose to produce quality mono-sex Nile tilapia Oreochromis niloticus

The 17α-methyltestosterone is the most common synthetic hormone used in male mono-sex production of Nile tilapia, Oreochromis niloticus. The current research aimed at finding out the most effective dose of 17α-methyltestosterone to produce quality Nile tilapia fry. Soon after absorbing the yolk sac, Nile tilapia fry was fed with a mixture of commercial fish feed and 17α-methyltestosterone for 28 days. Five doses of 17α-methyltestosterone, i.e., 0 mg, 50 mg, 60 mg, 70 mg, and 80 mg per kg feed, were used to treat tilapia that has been reared for additional 90 days to compare sex reversal, development, and survival rates. Both gonad histology and Squash test were performed to expose the sex percentage of O. niloticus accurately. The highest male 94.44% was obtained at 60 mg 17α-MT/kg feed dose followed by 91.67%, 88.89%, 86.11%, and 47.22% at 70, 80, 50, and 0 mg 17α-MT/kg feed dose. The groups treated with 17α-methyltestosterone hormone showed superior growth performance in comparison to the control group. The highest weight (14.62 ± 0.59 g) and length (92.18 ± 3.01 mm) were found at 60 mg dose whereas the lowest weight (8.64 ± 0.38 g) and length (70.17 ± 3.75 mm) were in the control group. The group given 60 mg 17α-MT feed represented the highest survival rate (84.10%) among other hormone-treated groups. The study disclosed that 60 mg 17α-MT/kg feed might be treated as the optimal dose for producing quality mono-sex male tilapia in the commercial hatchery.

GROWTH COMPARISON OF MONO AND MIXED-SEX GIANT FRESHWATER PRAWN (MACROBRACHIUM ROSENBERGII, DE MAN) AND STOCKING OPTIMIZATION OF MALE MONOSEX FARMING

Most often male freshwater Prawn (Macrobrachium rosenbergii) exhibits higher growth compared to the female counterpart. The current study has been conducted to evaluate the production performance and the survival rate of mono-sex male freshwater prawn culture compared to mono-sex female and mixed-sex culture. Conjointly the study also appraises the production competence of mono-sex male M. rosenbergii at different stocking densities. The experiment was conducted in two different phases. The first experiment comprised of three treatments, viz. mono sex male (T1), mono sex Female (T2) and both male & female (T3) with the same stocking density (3 in d/m2) and maintaining the sex ratio 100% male and female for T1 and T2, and 50:50 ratio for T3. The second experiment was conducted with all-male prawn (100% male) with three different stockings densities (i.e. 1, 2 and 3 in d/m2 successively as D1, D2 and D3). The results showed that in the first experiment, mono-sex males performed better growth, survival and production than mono-sex females and mixed-sex populations. In the second experiment, the highest individual growth was found to be 57.81±0.12 g in D1, 52.22±0.14 g in D2 and 40.97±0.1g in D3. Similarly, D1 showed the highest survival compared to D2 and D3. In contrast, the highest production (888.05±9.05 kg/ha) was found in D2, followed by D3 (826±42.07 kg/ha) and D1 (496.18±34.86 kg/ha). Hence, this research suggests practicing mono-sex male M. rosenbergii culture at stocking of 2/m2 for accomplishing maximum profits.

Histological changes in the gills, livers and muscles of Oreochromis niloticus fed with steriod, natural hormone and pawpaw seed based diets

This study was conducted to evaluate the histological changes of 17αmethyl-testosterone (MT), wet testes of bull (Bos indicus), boar (Sus domesticus), bull/mud catfish testes (B. indicus/C. gariepinus) and pawpaw (Carica papaya) seed powder-based diet on the Nile tilapia fry in an indoor experimental pond. Histological changes and efficacies in producing monosex males were determined after four months. Fifty-five fry were assigned randomly to three experimental ponds in triplicates. Five experimental feeds composed of soya-bean, fish meal, wheat bran, cassava flour were formulated by adding 0.06g of 17α- methyl-testosterone, 17.47g of bull wet testes, 25.59g of boar wet testes, 20.48g of bull/catfish and 20g of pawpaw seed powder per kg of feed to group 1, 2, 3, 4, 5 respectively. Obtained results from the morphological examination revealed a significant difference (p < 0.05) in phenotypic males of the Nile tilapia fry fed with the experimental diets. The highest indistinct percentage was recorded in the 17αmethyl-testosterone-treated diet while the lowest was recorded in diets 3 and 4 with no significant differences. All the groups showed histopathological differences in the livers, gills, and muscles. However, the liver histology of groups 1 and 5 showed central vessels that are mildly congested with abundant glycogen vacuolation and somewhat fat infiltration, while the histology of the muscles of group 5 showed pathological lesions including moderate to severe necrosis. These alterations can be considered an indication of the performance and health of fish in monosex culture medium indicating effects of plant extract and MT.

Growth performance of male monosex and mixed sex Nile tilapia (Oreochromis niloticus L.) reared in cages, Lake Victoria, Kenya

Growth performance of 17 alpha-methyl testosterone treated monosex and hormone untreated mixed sex tilapia was done for a period of 180 days in cages adjacent to Lwanda Disi beach, Lake Victoria, Kenya. Mixed sex Nile tilapia is known for frequent spawning in culture systems, resulting to fish with varied sizes and stunted growth. To attain male monosex fingerlings, the newly hatched fry were sex reversed by feeding them a diet laced with 17-alpha-methyl testosterone hormone for 21 days. Thereafter, the fry were fed 40% crude protein (CP) diet until stocking into cages. Mixed sex fry of same cohort were fed 40% crude protein starter diet until the time of stocking. A total of 6 cages (2×2×2 m) were randomly stocked with 1000 male monosex and mixed sex fingerlings. The individual mean (± SD) weight at stocking was 9.5 ± 0.06 g and 8.8 ± 0.08 for monosex and mixed sex, respectively. The experimental fish were fed starter diet 40% CP at 10% of body weight for the first two months. From the third month till the end of the experiment, the fish were fed 30 CP diet at 3% of body weight. Measurement of fish total length, body weight and selected water quality parameters was done once a month. There was a significantly higher (P < 0.05) mean body weight gain (BWG), specific growth rate (SGR) and condition factor (CF) for male monosex fish. Conversely, Feed conversion ratio (FCR) was significantly higher (P < 0.05) in mixed sex Nile tilapia. Survival rates (%) and water quality parameters did not differ between the groups. Though the mixed sex Nile tilapia did not reproduce in cages they performed poorly compared to male monosex.

Genital reversal of betta fish by immersion using steroid extract of sea urchins

Sea urchin, Diadema setosum is a potential fishery commodity with high economic value. It contains a steroid compound as an aphrodisiac in male monosexes (masculinization). In aquaculture usually used 17α-methyl testosterone, but it was difficult to decompose or it contaminated with carcinogens and pollutants. Therefore, it needs to be replaced with safer natural hormones from sea urchin. Betta sp. is an ornamental fish with high demand because of its colorful, diverse tail shapes, and price of male is higher than female, so that male cultivation is beneficial. This study aimed to utilize steroid compounds of sea urchin gonad extracts in masculinization of betta fish. In particular, it is to examine the steroid compounds by providing different doses and soaking times to the formation of male. The study was conducted using a completely randomized design method which was further classified into two stages. In first stage, the soaking dose was 0, 2, 4, 6 and 8 mg L-1 for 12 h, while in stage II, the immersion duration was 0, 12, 18, 24 and 30 h at a dose of 4 mg L-1 in larvae aged 2 weeks. Each treatment was repeated 3 times, and data were analyzed using Anova as well as with the LSD test at the level of 5%. The results showed that on the immersion in dose of 4 mg L-1, the highest male individual of 84.10% was formed. Also, a dose of 4 mg L-1 was significantly different from the control and 6 mg L-1, but it was not significantly different from that of 2 and 8 mg L-1. The difference in immersion time significantly affected the success of male monosex formation and the duration of 12 h in dose of 4 mg L-1 sea urchin extracts showed the highest percentage of 84.00%.

Monosex male formation of juvenile redclaw crayfish using natural steroid hormone from gamma sea cucumber and different doses of honey bee

In a new commercial commodity aquaculture, tropical freshwater crayfish Cherax quadricarinatus, it is known that female has a slower growth rate than male. One way to increase production rate is through monosex cultures comprising all-male population by using genital reversion technique. This biotechnology method can be applied by using hormones and natural products. The natural hormones extracted from gamma sea cucumber, Stichopus variegatus has bioactive substances including steroid compounds, while honey bee contains chrysin compounds that act as aromatase inhibitors. Therefore, the combination of both substances expected can increase in testosterone level and accelerate production in the male monosex population of juvenile crayfish. The purpose of the study is to determine the most effective dose of honey bee in masculinization of juvenile freshwater crayfish combined with 2 mg. L−1 steroid extract of gamma sea cucumber. Furthermore, a Completely Randomized Design (CRD) was designed in the experiment with five different dose of honey bee treatment and dipping method in 2 mg. L−1 steroid extract of gamma sea cucumber for 18 h. Each treatment with four replications. The highest male formation was found in the dose of 20 ml. L− 1 honey bee at 83.75% and the lowest was in control. The present of honey bee at different doses in 2 mg. L−1 of gamma steroid extract did not significantly give an effect on percentage of female, intersex formation, survival, and growth rate of juvenile redclaw crayfish.

Efficacy of cyanobacterium Anabaena sp. as a feed supplement on productive performance and immune status in cultured Nile tilapia

The purpose of this work was to research the impact of N2- fixing cyanobacterium Anabaena sp. supplementation in the diet or as a culture in the fishpond of Nile tilapia. The growth performance and chemical analysis of fish body were investigated before challenging with Aeromonas hydrophila (.A. hydrophila). While biochemistry of the serum, immunity, and health status of Nile tilapia were investigated before and after the challenge test. Oreochromis niloticus (monosex males) were randomly allotted into three groups, according to Anabaena supplementation in the fish diet or pond. Groups including, a control group was provided with the experimental diet without supplement, the AM (Anabaena meal) group was provided with the experimental diet enclosure Anabaena (15 g/100 g rations), and the A (Anabaena cultivated in the pond) group was provided with the experimental diet but Anabaena was cultivated in the pond. The results showed that both ways of Anabaena supplementation significantly (P ≤ 0.05) improved growth performance parameters and increased protein in body composition before A. hydrophila challenge compared with the control. On the other hand, the serum biochemical parameters and immunity status of Nile tilapia significantly (P ≤ 0.05) improved before and after experimental challenge.

Effect of Iron Nanoparticles on the Development of Fish Farm Feeds

Two hundred and seventy monosex males Nile Tilapia (Oreochromis niloticus) with an average body weight of 16.65±0.2 g/fish were used to investigate the effect of dietary replacement of inorganic iron by different levels of Fe-NPs on growth performance, body composition and health status of A. hydrophila challenged Nile tilapia fish. Fish maintained on 30% protein level, Six different experimental diets supplemented with 0.0 (T1), 85.0 mg inorganic Fe/kg (T2) and 85.0, 63.75, 42.5 and 21.25mg Fe-NPs/kg (T3-T5) were fed to triplicates groups of fish. It was found that the final body weight, weight gain, SGR, FCR and PER were significantly improved in the fish fed on the iron-supplemented diets compared to those fed on the iron-deficient diet (T1). Blood pictures and serum biochemical were significantly increased before and after A. hydrophila infection in the iron-supplemented groups compared to the iron-deficient diet group. The dietary administration of iron NPs improved the antioxidant enzymatic activities (CAT and TAC) irrespective of the different iron sources in the basal diet. Moreover, it was observed that the diets containing 63.75 and 42.5 mg/kg of Fe-NPs exhibited the best survival rate compared to the other groups.

Decreasing duration of androgenic hormone feeding supplement for production of male monosex in tilapia (Oreochromis spp.) fry

Decreasing duration of androgenic hormone feeding supplement for production of male monosex in tilapia (Oreochromis spp.) fry

Effect of phytase enzyme on growth performance, serum biochemical alteration, immune response and gene expression in Nile tilapia

The present study aimed to investigate the effect of low phosphorus diet with or without different levels of phytase enzyme supplementation on growth performance, body composition, nutrient retention efficiency, gene expression, and health status of A. hydrophila challenged fish. A total of 240 monosex males of Nile tilapia (Oreochromis niloticus) with an average body weight of 23.19 ± 0.15 g/fish were used. Fish were randomly chosen and divided into 4 equal groups (60 fish per group), with 3 subgroups containing 20 fish as a replicate. Group 1, was fed on a diet containing 100% P, group 2, was fed on a diet containing 50% P, group 3 and 4, were fed on low P with 500 or 1000 units of phytase/Kg respectively. It was observed that the 50% phosphorus diet significantly reduced body weight, feed intake, feed conversion ratio (FCR), and protein efficiency ratio (PER) compared to Nile tilapia fish fed on the diet containing 100% phosphorus. In contrast, fish fed on the diet containing 50% phosphorus supplemented by 500 or 1000 phytase units/kg significantly (P ≤ 0.05) increased final body weight (FBW), total body gain (TBG), average daily gain (ADG), and weight gain compared to Nile tilapia fed on the same diet or fed on the diet containing normal phosphorus without phytase supplementation. Different phosphorus and phytase supplementation levels had no significant effect on serum total protein, albumin, and globulin concentrations, meanwhile, phytase supplementation increased serum calcium and phosphorus levels. Nile tilapia fed on phytase supplementation had an increase in body protein, lipid content, and nutrient utilization efficiency compared to Nile tilapia fed on the diet containing 100% phosphorus. Nile tilapia fed on low dietary phosphorus showed an increase in mortality after infection and a decrease in phagocytosis and neutrophil compared to fish fed on normal phosphorus. Phytase supplementation, made immune response parameters return to its normal values and the pathological lesions of liver, spleen, stomach, and intestine were reduced. Moreover, normal phosphorus significantly up-regulated lipoprotein lipase (LPL) mRNA expression and down-regulated fatty acid synthase (FAS) mRNA in Nile tilapia's liver while low phosphorus with or without phytase supplementation reduced LPL expression and relatively up-regulated FAS.

Social factors and aromatase gene expression during adult male-to-female sex change in captive leopard grouper Mycteroperca rosacea

Social factors and aromatase gene expression in the leopard grouper Mycteroperca rosacea was studied when captive fish were separated by sex during the reproductive (April–June) and post-reproductive (July–September) seasons. Monosex females, monosex males, and mixed-sex, held in social sextet units were analyzed for sex steroids throughout confinement. At the end of the experiment, the gonad-sex was defined by histology, and gonad and brain aromatase gene expressions were quantified. Only males held in the monosex social units changed sex. Histology showed one male remained unchanged, six were found in a transitional sexual stage, in which two had intersex-predominantly-testes, and four had a more defined intersex ovo-testes pattern, and 11 were immature de novo females (neofemales). Neofemales and most intersex fish did not survive. In spring, 11-ketosterone showed a specific male profile, which suggests that male-to-female sex change was not triggered during the reproductive season. The low steroid levels in summer made it impossible to associate the sex change to a gonad hormonal shift; in September, gonad aromatase gene expression was not significantly different among groups. However, brain aromatase expression in intersex fish was significantly higher than monosex females, mixed-sex females, and neofemale groups. These results suggest that in the absence of female hormonal compounds, and at a time when male gonad steroidogenesis was diminished, the brain mediated male-to-male social-behavioral interactions, including stress, by increasing aromatization, resulting in derived intersex-male, which triggered more aromatization, followed by a sex change.

Những thành tựu trong nghiên cứu chuyển giới tính tôm càng xanh (Macrobrachium rosenbergii De Man, 1879)

This review synthesized studies on sex determination, scientific basis, approaches, and achievements in sex reversal of giant freshwater prawn (GFP) (Macrobrachium rosenbergii) around the world. GFP has a ZW sex determination system, where sex chromosomes are homozygous (ZZ) in males and heterozygous (ZW) in females. Sex differentiation of this species is controlled by protein-like hormone of the androgen gland. Males whose androgen gland is ablated (andrectomy) or in-activated by using RNA interference (RNAi) will develop to neo-females. Mating of these neo-females with normal males produces monosex males. These approaches have been applied successfully in commercial farming of GFP. However, the use of artificial hormone such as 17 α-methyltestosterol was not successful in sex reversal of GFP.

&lt;b&gt;Behavioral profile of &lt;i&gt;Macrobrachium rosenbergii&lt;/i&gt; in mixed and monosex culture submitted to shelters of different colors

Current research analyzed the behavioral activities of Macrobrachium rosenbergii and its preference for colored shelters in male monosex, female monosex and mixed culture. Ten shrimps m -2 were maintained in eight 250-L aquaria. Three artificial shelters, colored red, black and orange, were placed in each aquarium. Four aquaria were maintained in light/dark photoperiod respectively between 6h00 am and 6h00 pm and between 6h00 pm and 6h00 am, whereas the other four aquaria were submitted to an inverted photoperiod. The animals were observed for 30 days by Focal Animal Method for 15 minutes, with instantaneous recording every 60 seconds, at six different instances within the light and dark phases. Preference for black shelters occurred in male monosex and mixed cultures, whereas red and orange shelters were the preference of female monosex. M. rosenbergii kept in the shelter mostly during the light phase in male monosex and mixed populations. Results suggest that black, red and orange shelters may improve the animals' well-being in the culture since aggressive encounters would decrease, especially during the light phase.

INTENSIVE DIFFERENT STOCKING DENSITIES OF NILE TILAPIA, Oreochromis niloticus AND SILVER CARP, Hypophthalmichthys molitrix UNDER MONO-OR POLYCULTURE SYSTEMS IN FLOATING NET CAGES REARING IN MANZALA LAKE, Egypt

This experiment was designed in order to study the effect of intensive rearing of mono-sex Nile tilapia and Silver carp under mono-or polyculture systems at different stocking densities in floating net cages. Fish were male mono-sex Nile tilapia with an average initial body weight (19.30 g) and Silver carp with an average initial body weight (73.6 g). The experimental fish were adapted for one week in floating net-cages and then distributed randomly into five experimental cages. The first cage was stocked with Nile tilapia, at a rate of 30 fish / m3, while the 2nd, the 3rd and 4th cages were stocked with different densities of Nile tilapia with Silver carp, at a rate of 30 fish / m3 and the fifth cage was stocked with Silver carp only at a rate of 6 fish / m3. All fish groups were feed the same artificial pelleted diet (except 5th group fed natural water food). The diets were contained of 26.58% crude protein and gross energy 410.35 Kcal/100g DM, and offered twice daily (at 8.30 a.m. and 15.00 p.m.). The feeding rate represented 4% of mass body weight during all experimental periods. The main results showed that the best treatment was the monoculture of mono-sex Nile tilapia (30 fish / m3), then followed by the polyculture (88% Nile tilapia) and (12% Silver carp) in most of the examined traits as well as in the economic efficiency. The obtained results showed also that the intensive monoculture systems of silver carp had the lowest economic efficiency related to the only natural food in water only. The present obtained results lead to the importance using the balanced pelleted complete diet for feeding tilapia fish especially under intensive cultured (monoculture); as well as, depending of green water for fed Silver carp in intensive monoculture. Also, showed the superiority of stocking densities in polyculture system were 88% and 12% for Nile tilapia and Silver carp, respectively As well as from environmentally point of view, it could be concluded that the controlling on different source of water pollution in Manazala Lake are very important to get high quality and safety fish production.

IMPACT OF DIETARY PROTEIN AND HYDROYEAST AQUACULTURE® LEVELS ON GROWTH, FEED EFFICIENCY, PHYSIOLOGICAL, AND HISTOMETRIC RESPONSES OF Oreochromis niloticus FINGERLINGS

Tilapia is one of the most important farmed fish in the world. The main objective of this study was to evaluate the effects of supplementation the graded levels (0, 5, 10, and 15 g / kg diet) of a new commercial probiotic Hydroyeast Aquaculture® to low crude protein (CP) levels (20 and 25%) in diets of male monosex Oreochromis niloticus fingerlings for 14 weeks, regarding their growth performance, feed utilization, carcass composition, hematological, and histometeric parameters of the intestine. Fish with an average initial body weight (7.5 ± 0.001 g) were distributed into eight treatments (three replicates per treatment). Fish in each treatment were stoked at 5 fish / aquaria (90×40×35 cm).The results revealed that the high levels of CP (25%) and probiotic (15 g / kg diet)had positive significant (P ≤ 0.05) effects on fish growth performance parameters, feed utilization, fish carcass composition (DM, CP, and EC), hematological constituents (hemoglobin, red blood cells, packed cell volume, and blood platelets) and intestine histometric parameters compared with other treatments, but the interaction between them was not significantly affected on all the above parameters. Therefore, it could be concluded that the high level of probiotic 15 g Hydroyeast Aquaculture® / kg diet is useful with low dietary CP level (25%) in feeding fish at early age stage for enhancing the production performance, physiological responses and histometeric parameters of the intestine of male monosex O. niloticus fingerlings, thus this level of probiotic may lead to increase the economic efficiency at large scale in the fish farms.

COMPARATIVE GROWTH PERFORMANCE OF MALE MONOSEX AND MIXED SEX NILE TILAPIA (Oreochromis niloticus L.) REARED IN EARTHEN PONDS

Comparative growth performance of male monosex and mixed sex Nile tilapia (Oreochromis niloticus ) was conducted in six earthen ponds each measuring 150 m 2 at the Kenya Marine & Fisheries Research Institute (KMFRI), Kegati Aquaculture Research Station. Male monosex and mixed sex of O. niloticus juveniles at an average weight of 12.2 ± 0.02 g and average length of 7.6 ± 0.02 cm were collected from nursery production ponds. The male monosex juveniles were obtained by feeding newly hatched juveniles with feed dosed with 17 α methyl testosterone hormone for a period of one month. Stocking was at 3 juvenile