Mono Sex Research Articles

Broccoli Partially Lowers Oxidative Stress, Histopathological Lesions and Enhances Antioxidant Profile of Mono Sex Tilapia Exposed to Zinc Oxide Nanoparticles

Broccoli Partially Lowers Oxidative Stress, Histopathological Lesions and Enhances Antioxidant Profile of Mono Sex Tilapia Exposed to Zinc Oxide Nanoparticles

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.

Valorization of the duckweed (Spirodela polyrhyza) in the feeding of mono sex male fry of Oreochromis niloticus: Zootechnical performance and economic profitability

Valorization of the duckweed (Spirodela polyrhyza) in the feeding of mono sex male fry of Oreochromis niloticus: Zootechnical performance and economic profitability

Impact of Biofloc technology on growth performance and biochemical parameters of Oreochromis niloticus.

In the present study, the experiments were conducted during the period from June to October 2019 (20-weeks) to evaluate the effect of Biofloc technology (BFT) on mono sex Nile tilapia, Oreochromis niloticus fingerlings. It was focused on water quality, growth parameters, hepatosomatic index (HIS), spleenosomatic index (SSI), Hematology, and biochemistry. Triplicated treatments were designed, two Biofloc treatments with two fish densities (12 &16 fish/200 L tank) vas two control groups. All treatments were fed with 3% of body weight in two equally divided meals. Rice brane and Molasse (1:1) were added as a carbon source to Biofloc treatments twice daily after one hour of main meals. Results indicated that total ammonia-N and Nitrite-N were significantly decreased at Biofloc treatments. Biofloc treatments showed significantly high average final body weight, better feed conversion ratio (FCR), and one-ninth water consumption. Biofloc addition had generally no significant difference of hematology, biochemistry, and hepatosomatic index (HSI), while spleenosomatic index (SSI) was significantly increased at high density only. It could be concluded that Biofloc treatments improve water parameters stability and fish growth performance while it decreased water consumption. High density (16 fish/200 L) is a more yield productive treatment.

PENINGKATAN NISBAH IKAN NILA JANTAN MENGGUNAKAN 17α-METILTESTOSTERON MELALUI PAKAN

Keberhasilan maskulinisasi pada ikan nila menunjukkan bahwa penggunaan hormon 17α-metiltestosteron (MT) lebih efektif dibandingkan suhu. Akan tetapi penggunaan hormon dengan cara pemberian melalui pakan belum menunjukkan hasil yang lebih baik dibandingkan dengan perendaman larva. Padahal secara aplikasi melalui pemberian pakan lebih mudah dilakukan. Oleh karena itu, pada penelitian kali ini akan dilakukan pemberian hormon melalui pakan dengan waktu percobaan pemberian pakan melebihi waktu kritis tertinggi, yaitu selama 30 dan 50 hari. D'Cotta et al. (2007) dan Ijiri et al. (2008) menyatakan bahwa waktu kritis untuk dilakukannya perubahan jenis kelamin pada ikan tilapia adalah 9-15 hari setelah pembuahan / day post fertilization / dpf. Tujuan yang ingin dicapai dalam penelitian ini adalah untuk mendapatkan periode waktu pemberian hormon 17α Metiltestosteron yang optimal melalui pakan untuk menghasilkan ikan nila monosex jantan.Perlakuan menggunakan hormon 17α-metiltestoteron dengan dosis 60 mg /kg dengan perlakuan lama pemberian pakan 0, 30 dan 50 hari. Pengaruh lama waktu pemberian pakan mengandung hormon di uji menggunakan uji anova pada selang kepercayaan 95%. Hasil yang diperoleh menunjukkan bahwa penggunaan 17α-metiltestoteron dalam sex reversal dengan dosis 60 mg/kg pakan dengan lamawaktu pemberian 0, 30 dan 50 hari menunjukkan adanya perbedaan jumlah kelamin ikan nila jantan yang dihasilkan. Akan tetapi tidak terlihat adanya perbedaan nyata pada nisbah kelamin jantan pada perlakukan 30 dan 50 hari pemebrian pakan. Sehingga dapat disimpulkan bahwa pemberian pakan hormon 17α-metiltestoteron melalui pakan selama 30- 50 hari setelah penetasan dapat meningkatkan nisbah kelamin jantan pada ikan nila lebih dari 80%.

AN ASSESSMENT STUDY OF GROWTH PERFORMANCE AND GONADS DEVELOPMENT OF MONO SEX NILE TILAPIA IN DIFFERENT AGE STAGES DURING THE PRODUCTION PERIOD

The objective of this study was to follow up the growth performance and gonads development of sex reversed male Nile tilapia. Fish fed commercial diet contained 30% crude protein at a rate of 3% of the biomass and 10 fish were randomly taken biweekly during the experimental period (16 weeks). Growth performance, feed utilization and survival rate were calculated. Histological examination of the gonads was done every two weeks to follow the growth and development of the gonads. Results showed positive interactions between growth parameters and reproductive development during different periods of fish productive cycle. Histological examination illustrated that during early ages, testicular sections of mono sex male’s tilapia had abnormal architecture with deterioration of germinative tissue. Despite abnormal testis texture, fish started spermatogenesis, a step toward puberty when their body weight reached 29.16g. As fish reached 4-5 months, male start to recover their testes normal structures and at age of 5.5-6 months, testicular sections appeared normally as pointed out by firmed testicular lobules, existence of all germ cell types and the intensively stored spermatozoa in testicular lumen and testicular ducts, confirming the full maturity of males. Based on the obtained results, it can clearly conclude that there is a relationship between age, body weight and development of sexual glands. It has also been shown that the hormonal treatment of tilapia seeds in the early stages for production of mono sex (all males) leads to a marked deterioration in the testes structure, continues near the fish enters the sexual maturity. At a later age, males can overcome this deterioration, restore the histological structure of the testes and achieve full sexual maturity at the age around from 5.5 to 6 months.

EFFECT OF DIETARY PROTEIN LEVELS AND SEX ON GROWTH PERFORMANCE, FEED UTILIZATION AND BODY COMPOSITION OF NILE TILAPIA (OREOCHROMIS NILOTICUS) FRY CULTURED IN HAPS.

The effect of dietary protein levels (35%, 40% and 45%) on growth, survival, feed utilization and body composition of mono sex and mixed sex of Nile tilapia; Oreochromis niloticus L. fry was investigated. Fish were fed frequently to satiation for 7 days a week for 56 days. Results showed that fish growth was significantly affected by protein level. The highest growth performance of fry were obtained with 45% protein diet and the poorest one was obtained with 35% protein diet in both mono and mixed sex Nile tilapia, Oreochromis niloticus fry. Mono sex tilapia were reared in hap in earthen pond showed the highest weight gain, specific growth rate, feed conversion ratio, feed efficiency and protein efficiency ratio, while mixed-sex tilapia showed the lowest weight gain, specific growth rate, feed conversion ratio, feed efficiency and protein efficiency ratio. In conclusion, it was found that 45% crude protein had the highest growth performance parameters, feed utilization and economical evaluation for mono sex Nile tilapia (O. niloticus) fry under this experimental condition.

Optimization of Nile tilapia breeding schemes for monosex culture conditions in smallholder production systems

The aim of this study was to optimize the design of a nucleus Nile tilapia breeding program for harvest weight, growth rate and survival in the presence of genotype by environment interaction with monosex (MS) culture of all-male fish. A nucleus breeding program was deterministically simulated using pseudo-BLUP selection index theory, implemented in SelAction. First, we investigated the rates of genetic gain for growth rate, expressed as TGCms using different selection indexes with varying degrees of genotype by environment interaction (G×E), expressed as the genetic correlation (rg) between the nucleus and a monosex production environment. Selection strategies were (1) mass selection in nucleus only, (2) Best Linear Unbiased Prediction (BLUP) with full/half sib information from the nucleus fish only, and (3) BLUP with information from full and half sibs in the nucleus and in the monosex production environment. In the second step, we extended the breeding goal to include harvest weight (HWms) and survival (Sms) to derive desired weights and genetic gains for these breeding goal traits. Finally, we maximized genetic gains in Sms while restricting the loss in TGC to 5%. Results: the presence of G×E lowered accuracy of selection (rIH) which led to a loss in genetic gain for TGCms. At rg of 0.7 and less, incorporating half sib information from monosex sibs into the selection index resulted in higher genetic gains of TGCms. Using 8 offspring in the nucleus as selection candidates and 32 offspring in monosex production environment, resulted in highest accuracy with lowest rates of inbreeding. This index had the highest relative genetic gains in all rg tested, implying that this index is least sensitive to G×E. Phenotypic variance ratio had no effects on rIH but had effects on predicted genetic response. Maximizing gains for HWms and Sms caused a large reduction of genetic gain in TGCms. However, allowing a 5% loss of genetic gain in both TGCms and HWms resulted in a 33% increase in genetic improvement of Sms. A breeding goal that maximizes survival while restricting loss in TGC to 5% had the highest response in US$. Statement of relevanceThis is the first study that presents optimization of Nile tilapia breeding schemes for monosex culture conditions in smallholder production systems of the tropics.

Growth Performance of Mono Sex and Mixed Sex Climbing Perch (Anabas testudineus)

Many factors influence fish growth like rearing by sex. This study aims to determine the growth of theClimbing perch of the different sexes. This research was conducted at hatchery business unit at MulyaPlaju, from May to July 2015. Fry spawning fish came from the wet Laboratory Faculty of Agriculture,University of Muhammadiyah Palembang. They were maintained separately between the male and thefemale and the gender-mix between male and female, reared in nets with a density of 30 individualseach net; each treatment was repeated three times. During the research, fry feed used artificial feedwith 30% protein compotition. The results showed that there was growth of female was faster than ofmale and of mixed sex. The growth of fish was 1,40 cm and weight of 4.56 gr, while survival rate ofthem was 100%. Keywords : growth, Anabas testudineus, mixed sex, mono sex

Effect of partial and total replacement of fishmeal with sand smelt (Atherina boyeri) meal in practical diets for mono sex Nile tilapia (Oreochromis niloticus) fingerlings.

Effect of partial and total replacement of fishmeal with sand smelt (Atherina boyeri) meal in practical diets for mono sex Nile tilapia (Oreochromis niloticus) fingerlings.

NUTRITIONAL STUDIES ON PARTIAL AND TOTAL REPLACEMENT OF SOYBEAN MEAL WITH GUAR MEAL (CYAMOPSIS TETRAGONOLOBA (L.) IN NILE TILAPIA (OREOCHROMISNILOTICUS) DIETS

The main objective of this study was to evaluate the effect of partial and total(0%, 25%, 50%, 75%, and 100%) replacement of soy bean meal (SBM) protein by guar meal (Cyamopsis tetragonoloba ) (GM) protein in commercial diets on water quality, ,survival rate %, growth performance, feed utilization , whole body composition , physiological parameters and economic efficiency of Nile tilapia, Oreochromis niloticus fry. Fish fry with an average initial weight of 0.825± 0.01 g/fish were stocked at a rate of 10 fish/aquarium (100L water) for 84 days experimental period. Five experimental diets were formulated to be isocaloric (454.34 kcal GEl/100 g dry matter, DM) and isonitrogenous (30.25% crude protein, CP %). The results of this study revealed that, the highest (P≤0.01) final weights, specific growth rate, protein and nutrient utilization were recorded by GM 25 and 50% groups followed by the control group and the GM 75 and100% groups, respectively. Therefore, these results suggest that the replacement of 25 and 50% of SBM by GM had a significant increase on fish growth performance (final body weight, average body weight and Specific growth rate %) , feed and nutrient utilization respectively , however replacing of the higher GM levels (75 or 100%) significantly (P≤0.01) reduced them . The group fed on 50% GM exhibited comparable growth performance to those fed SBM based diet. Carcass CP% was significantly (P ≤ 0.01) increased with the increase of dietary GM up to 50% and decreased with 75% and 100% levels. Dietary GM levels does not show any significant effects on carcass ether extract (EE %). Increasing GM up to100% increased carcass ash content significantly (P ≤ 0.01) while energy content (EC) values were decreased. Hematocrit and hemoglobin values (hematological parameters) were almost decreased proportionally with increasing the dietary GM with the largest declines in groups fed on 75-100% GM levels. Values of serum transaminases (aspartate aminotransferase, AST and alanine aminotransferase, ALT) were almost increased with the increase in GM level as a substitute for SBM in Nile tilapia diets. Therefore, these results suggest that up to 50 % of soy bean meal protein can be replaced by guar meal protein in mono sex Nile tilapia diets without any adverse effect on growth performance and feed utilization.

EFFECT OF DIET EXTRUDED TYPE ON GROWTH PERFORMANCE, FEED UTILIZATION AND ECONOMIC EFFICIENCY OF NILE TILAPIA IN COMMERCIAL FARMS

This study aimed to evaluate the effect of extruded diets (floating and sinking) on growth parameters, feed utilization and economic efficiency of Nile tilapia (Oreochromisniloticus) cultured in commercial farms. A total number of (100000) mono sex Nile tilapiafingerlings of 5.27 ± 0.01 g initial body weight in average were allotted randomly into four earthen ponds (two feddan/each). Two diets were used extruded floating diet (EFD) and extruded sinking diet (ESD), from zoo control company. The diets contained the same level of protein, carbohydrate and fat as formulation and ingredients of the experimental diets were the same. Each diet contained in average 27.37% CP and 4.57 kcal/g GE. Fish were fed pelleted extruded diet type at a rate of 3% of the total body weightand was adjusted every month intervals until harvesting. Results cleared that final mean weight and weight gain were significantly (P≤0.05) better with EFD, while lower values were recorded with ESD, but daily gain and specific growth rate insignificantly affected by diet type.Feed intake was significantly decreased with EFD. FCR values were significantly better with EFD than ESD. Survival rates insignificantly affected and ranged between 87.23 and 92.10%. Net returns and profit index were significantly high with EFD than sinking diet. In conclusion regarding to final weight, survival rate, net returns and profit index, the EFD was best feed if served suitable environmental condition specially low wind speed and lack of birds.

Intensive Cage Culture of Nile tilapia in River Nile Systems Canals in Egypt

A 28-week rearing trial was conducted in twelve one cubic meter cages with (30.2 ± 3.2 g/fish) Nile tilapia, Oreochromis niloticus mono sex males fingerlings, to test the feasibility of rearing Nile tilapia mono sex in floating cages placed in the River Nile systems, to find out the optimum stocking density per m 3 that could give maximum yield of market-size fish, also, the weight and length of fish at stocking and to determine the physico-chemical characteristics of the water of El-Bagoria canals at El-Hamoul, Menoufiya governate. Fish were fed a least cost diet containing 30.2% crude protein and 4600 kcal /kg diet. The results revealed that Nile tilapia average weight 30.2 g/fish with 150 fish /m 3 as stocking density were adequate for rearing. These fish gave the best both of average weight gain of 117 g/fish and total production of 22.1 kg/m 3 . The artificial food supplied with a crude protein content of 30.2 % is adequate for rearing Nile tilapia in running water systems. The physico-chemical property of the water of El-Bagoria canals was found to be adequate for rearing of Nile tilapia in cages.

Effects of Salinity and Ultraviolet Radiation on the Bioaccumulation of Mycosporine‐like Amino Acids in Artemia from Lake Urmia (Iran)

We investigated the effects of salinity and artificial UV radiation on the accumulation of mycosporine-like amino acids (MAAs) in sexual and parthenogenetic Artemia from Lake Urmia. The nauplii hatched from the cysts were cultured until adulthood under two salinities (150 and 250gL(-1) ) and two light treatments (PAR and PAR+UVR) in the laboratory. Finally, the Artemia were analyzed for their concentration of MAAs. In most of the cases, the higher salinity level applied was found to increase the MAA concentrations in both Artemia populations significantly. The acquisition efficiency of MAAs in both Artemia populations increased under exposure to UVR-supplemented photosynthetically active radiation (PAR) compared to those raised under PAR, except for Porphyra-334. It was observed that combination of UV radiation and elevated salinity significantly increased the bioaccumulation of MAAs. Thus, the presence of these compounds in these populations of Artemia may increase their adaptability for living in high-UV and high-salinity conditions prevailing in Lake Urmia. Higher concentrations of MAAs in the parthenogenetic population of Artemia could be probably attributed to its mono sex nature and higher adaptation capacities to extreme environmental conditions.

Histopathological changes in Poecilia latipinna male gonad due to Tribulus terrestris administration

Tribulus terrestris is a traditionally known non-toxic aphrodisiac herb for maleness. It was experimented recently to understand the effect and mechanism on mono sex production in Poecilia latipinna. It would help to develop a new eco-friendly way to masculinize P. latipinna, since males have higher commercial value than females. The different concentration (100, 150, 200, 250 and 300 mg/L) of T. terrestris extract and a control were tested for their effect on sex transformation/reversal in P. latipinna by immersing the newly born young ones in the respective concentrations for 2 mo. The obtained results indicate that a dose dependant masculinization is obtained due to T. terrestris administration, which improved the male proportion. Histological results revealed that the testes of fish treated with T. terrestris extract contained all stages of spermatogenesis, clearly demonstrating that the administration of T. terrestris extract to P. latipinna stimulated spermatogenesis. Thus, it is discernible that 0-d-old hatchlings of P. latipinna exposed to T. terrestris extract orient/reverse their sex more towards maleness besides yielding better growth and spermatogenesis which is a mandate for fancy fish industry.

Effect of chelating agent edta (ethylene diamine tetra acetic acid, disodium salt) as feed additive on controlling heavy metals residues in Sarotherodon galilaeus fish

The study was undertaken in order to determine the effect of chelating agent EDTA as feed additive on controlling heavy metals (Pb&Cd) which cause some dangerous diseases and its impact on growth performance, feed and protein utilization, carcass composition and biochemical parameters in mono sex Galilee Tilapia fingerlings were studied. Galilee tilapia fingerlings were collected from El-Zaheria village, Abo- Hamad, Sharkia (recorded as polluted area) and analyzed for lead, cadmium and zinc contamination at the start of experiment. The fish were divided into 5 treatments EDTA (ethylene diamine tetra acetic acid, disodium salt) were included in the diets at a rate of 0.0, 0.5, 1.0, 1.5 and 2.0%. The diets were formulated to be iso-nitrogenous (30.19%±0.15 crude protein) and iso-caloric (4459.49± 85 kcal gross energy/kg diet). After that, the fish were randomly distributed into 15 aquarium (5 fish/aquaria) of Galilee Tilapia fingerlings, Each diet treatment was applied to triplicate groups (54.2± 0.99 g/fish) at rate six days of the week and the experiment extended for 49 days. The obtained results showed that, lead (Pb) and cadmium (Cd) concentrations were significantly decreased in all EDTA treatments in the whole body and fish flesh of Galilee Tilapia fingerlings compared with those at the start of the experiment and control group (E1, 0.0% EDTA) . The biochemical parameters were significantly improved at (P< 0.05). The uric acid and cholesterol levels were significantly decreased. The highest weight gain (WG), average daily gain (ADG), and specific growth weight (SGR) and protein and nutrient utilization at (P< 0.05) were recorded by E4 (1.5% EDTA) followed by E3 (1.0% EDTA), respectively. In conclusion the addition of EDTA to contaminated fish with heavy metals, reduced significantly Pb and Cd levels. The obtained results showed that all the tested biochemical parameters and growth performance, protein, nutrient utilization body carcass were improved due to EDTA application and the effects were more pronounced at 1.5% EDTA/ kg diet, which are considered as the optimum dose that improve the healthy status and growth parameters of fish in this experiment.

PARTIAL REPLACEMENT OF SOYBEAN MEAL WITH BLACK SEED AND ROQUETTE SEED MEALS IN NILE TILAPIA (Oreochromis niloticus) FINGERLINGS DIETS.

Black seed meal (Nigella sativa) and roqutte seed meals (Eruca sativa) were tested to replace soybean meal (SBM) in diets for mono sex Nile tilapia fingerlings (Orecreomis niloticus). Nine isonitrogenous (30% CP), isocaloric (460 kcal GE/100g) diets were formulated to contain black seed (BSM) and roquette seed meals (RSM) as a partial replacement of soybean meal at different levels (0, 5, 10, 15 and 20%) forming 9 treatments, 4 with BSM and 4 with RSM and the control. The diets were fed daily at a rate of 4 % of fish body weight in triplicate groups with 15 Nile tilapia fingerlings each (3.14g/fish), in 80 l glass aquaria for 90 days period. Data collected were on growth rate, feed utilization and body composition along with simple economic evaluation. Results of growth performance showed that SBM substitution with BSM and RSM were nearly similar. Survival rate was not affected greatly but it seems that all levels of BSM substitution were more favorable than the other RSM substitutions. As for feed utilization most treatments used showed similar results to the control. The 20 % RSM replacement (instead of SBM) showed the lowest values. Carcass CP content was not affects by all levels of BSM and 5 to 15% levels of RSM that substituted SBM. Carcass fat content showed no significant differences among all groups and the control group. The highest ash content in fish body was obtained by fish fed T9 diet which contained 20% RSM as a partial replacement of SBM. The present study suggest that BSM and RSM have were more economic efficiency when replacing SBM at levels of 20% and 15%, respectively in Nile tilapia fingerlings diets.

Effect of initial weight and stocking density on growth performance of mono sex nile tilapia reared in semi intensive system

he present investigation was carried out at Wady El Raian, Fayoum Governorate, Egypt in order to test the effects of initial weight and stocking density on growth performance and pond productivity of Nile tilapia (Oreochromis niloticus) in semi intensive system. The experiment was carried out in 12 earthen ponds each of a total area of one feddan (4200 m 2 ) to represent six treatment groups in replicates each. The first; second and third two ponds (T1; T2 and T3) were stocked with Nile tilapia fingerlings of an average initial weight of 9.6 g and stocking density 30; 40 and 50 thousands respectively. The second; fourth and sixth tow ponds (T4; T5 and T6) were stocked with Nile tilapia fries of 0.3g and stocking density 30; 40 and 50 thousands respectively. The fish were fed three times daily on a commercial diet containing 27% protein at a rate of 3% of fish biomass. The experiment lasted for 26 weeks from the start. Results obtained are summarized in the following: 1- Water quality (physical and chemical) lied within the permissible levels required for optimum growth and development of Nile tilapia. 2- The highest final weight was obtained by T4; T1; T2; followed in a significant decreasing order by T5; T4 and T6 respectively. 3- Averages of gain in weight; daily gain; specific growth rate and condition factor were influenced significantly with tilapia initial weight and stocking density. 4- Total fish production/feddan was the highest for 50 thousand fingerlings/feddan, stocking density followed by 40 and 30 thousand fingerlings/feddan. 5- The highest net returns were by the 30 thousand fingerlings/feddan stocking density (T1) and 40 thousand fingerlings/feddan stocking density (T2) due to the high contribution of super size and grade 1 fish in the harvest, compared to other densities and initial weights.

Nutrition evaluation of sesame seed meal, Sesamum indicum (L.) as alternative protein source in diets of juvenile mono-sex Nile tilapia (Oreochromis niloticus).

he main objective of this study was to evaluate the effect of partial and total replacement of fish meal protein by sesame seed meal (SSM) protein in commercial diets on growth performance, feed utilization and bodycomposition of juvenile mono sex Nile tilapia, Oreochromis niloticus (L.). Fish of an average initial weight of 0.60 ± 0.01 g were stocked in 15 glass aquaria (80 l each) at a rate of 15 fish per aquarium. Fish meal protein (18% of the diet) wasused as the sole source of animal protein in the control diet. Percent replacements of fish meal by sesame seed meal on the basis of crude protein were as follows: 0 % (control diet A), 25 % (diet B), 50 % (diet C), 75 % (dietD) and 100 % (diet E). All tested diets were almost isonitrogenous and fed at a rate of 4 % of fish body weight, and then gradually reduced to 3 % of the total fish biomass daily, for a period of 16 weeks. The results of this study revealedthat, fish fedon diet A (100 % FM) had the highest average body weight, specific growth rate (SGR), weight gain %, feed conversion ratio (FCR), and protein efficiency ratio (PER), but the lowest was obtained with fish fed diet E (100 %SSM). The same parameters of fish fed on diets B (25 % SSM) and diet C (50 % SSM) were not significantly different (P > 0.01) from those of fish fed on the control diet A. Proximate composition of the whole body moisture and ashcontents were not significantly affected (P>0.05) by the dietary treatments.Whole body protein contents for fish fed on diets B, C and D were superior to the control diet. Incorporation of sesame seed meal in the fish diets increasedsignificantly whole body fat content. Incorporation of sesame seed meal in the diets significantly increased apparent digestibility coefficients of crude protein, crude fat and energy. Therefore, these results suggest that up to 50 % of fishmeal protein can be replaced by sesame seed protein in mono sex Nile tilapia diets without any adverse effect on growth performance and feed utilization,body composition and digestibility.

Application of Hormones in Fish Culture

Methyltestosterone, when incorporated in the diet at a concentration of 1 ppm, accelerated the growth of goldfish (Carassius auratus), horai masu, a variant of rainbow trout (Salmo gairdneri), and kokanee (Oncorhynchus nerka). Simultaneous acceleration in the growth of the testes was also observed in some of the horai masu. Administration of 5 ppm methyltestosterone or diethylstilbestrol in the diet combined with injection of salmon gonadotropin was effective in accelerating the sexual maturation of rainbow trout. However, a concentration of 50 ppm methyltestosterone inhibited gonadal development if the treatment was initiated shortly after hatching and continued for a period of 5 mo. The fish thus treated were found to have threadlike gonads even after 3 yr. Courtship behavior and feeding behavior were also influenced by methyltestosterone treatment. The sex ratio of zebra fish (Zebrafario) and rainbow trout was altered when the administration of methyltestosterone was initiated just after hatching. This suggests a strong possibility of introducing sex reversal or mono sex culture in these important commercially raised fish. Results with the cobalt variant of rainbow trout, a fish lacking a complete pituitary and found only with immature gonads, suggest that this animal may be a promising model for future studies in fish endocrinology.