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. 2022 Dec 9;8(12):e12252. doi: 10.1016/j.heliyon.2022.e12252

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

Baadruzzoha Sarker a, Bipresh Das a, Shawon Chakraborty a, Mohammad Amzad Hossain a,∗, MM Mahbub Alam b, Sohel Mian a, Mohammed Mahbub Iqbal a
PMCID: PMC9758436  PMID: 36536906

Abstract

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.

Keywords: Oreochromis niloticus, 17α-Methyltestosterone, SGR, Dose optimization, Growth performance

Oreochromis niloticus; 17α-Methyltestosterone; SGR; Dose optimization; Growth performance

1. Introduction

Tilapia is a global candidate fish of great commercial significance and is currently the second largest farmed fish followed by carps in worldwide production (Hasan et al., 2021; Prabu et al., 2019). The world's total tilapia production reached approximately 6 million tons in 2020 (Guenard, 2020). The advantageous features of tilapia most importantly faster growth, extreme tolerance capacity to hostile environments, high disease resistivity along with high survival rate make it a predominant culture species (Alam et al., 2014; Dowidar et al., 2018; Hossain et al., 2022). However, the main obstacle in tilapia culture is its early sexual maturity and frequent spawning in the culture system (Lind et al., 2015). Overpopulation of tilapia, results in competition for food and eventually causes decreased production as well as profits. Producing male mono-sex seeds is the best solution to this problem (Beardmore et al., 2001; Omasaki et al., 2017). Besides, male tilapia has a higher growth rate compared to females (Lind et al., 2015). Because metabolic energy in male is used for somatic growth whereas in female large portions of metabolic energy is used for reproductive purposes (Lu et al., 2022; Snake et al., 2020). It has been reported that sex switched tilapia performed three times better growth when treated with ideal hormonal preparation (Kamaruzzaman et al., 2009; Mair et al., 1995). Besides, mono-sex stock ensures uniform harvest size and prevents immature courtship activities. Though numerous techniques have been introduced to generate male tilapia, hormonal sex reversal is still treated as the most popular and economically viable practice (Beardmore et al., 2001; Prabu et al., 2019). Therefore, oral administration of feed mixed with androgen hormone has been perceived as the most ideal technique for commercial and mass production across the world (Karaket et al., 2021; Ridha and Lone, 1990). In Bangladesh, mono-sex producers mostly use synthetic hormones (17α-MT) for the mass production of seeds (El-Greisy and El-Gamal, 2012; Kohinoor et al., 2003). By using inefficient doses (high or low), hatchery owners are incurring economic and resource losses (Bostock et al., 2022; Rouf et al., 2008). Employing overdose brings harmful issues to aquatic environments (Mlalila et al., 2015; Thanasupsin et al., 2021). Alternatively, lower dosages will produce a lower rate of mono-sex male Nile tilapia. Therefore, the current study was aimed at identifying the most efficient hormonal dose for mono-sex seed production along with confirming the best growth performance of seeds.

2. Materials and methods

2.1. Ethical approval and clearance

The Animals Ethics Committee of the Department of Fish Biology and Genetics, Sylhet Agricultural University, Sylhet-3100, Bangladesh, authorized the experimental design and animals utilization for this research project.

2.2. Study area

A private Tilapia Hatchery owned by BRAC located at Moulvibazar, Sylhet, Bangladesh had been selected to perform the field experiment (Figure 1). Laboratory analysis was performed at the Post-graduate Laboratory of the Faculty of Fisheries, Sylhet Agricultural University, Sylhet (Figure 1).

Figure 1.

Figure 1

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Location of the study area: A. Laboratory of Faculty of Fisheries (24°54′38.9″N 91°54′04.3″E) and B. BRAC Fish Hatchery, Sreemangal (24°18′20.2″N 91°40′47.3″E) (map modified from Islam et al., 2011).

2.3. Experimental design and diet preparation

The experiment was conducted for a period of 118 days where fry was treated with 17α-MT hormone for initial 28 days and reared further in hapas for 90 days. The rearing pond was 4050 m2 in size with 1.53 m average depth. A total of fifteen synthetic nylon hapas, covering 5 m3 size each, have been employed in 5 columns and 3 rows, and fixed tightly using bamboo poles followed by the previous description (Argue, 1995; Barman and Little, 2011). Four treatments and one control each with 3 replications were used for this experiment. The powdered form of 17α-MT hormone was dissolved in 95% ethanol and kept overnight for evenly mixing and 250 ml ethanol was used for producing per kg hormone-treated feed based on the protocol from Vinarukwong et al. (2018). Four doses of 17α-MT were used for this experiment i.e., T1 (50 mg MT/kg feed), T2 (60 mg MT/kg feed), T3 (70 mg MT/kg feed), and T4 (80 mg MT/kg feed). Briefly, hormone mixed ethanol was poured over the commercial feed (Mega feed, Spectra Hexa Company, Bangladesh) in a locally modified motorized machine that mixed the hormone homogeneously with feed. After that hormone mixed feed was dried at room temperature for 24 h to evaporate the ethanol efficiently and then kept in airtight sacs. Commercial nursery feed (Mega feed, Spectra Hexa Company, Bangladesh) was used as artificial feed and the proximate composition of feed was analyzed at the Aquaculture laboratory of Bangladesh Agricultural University (BAU) and presented as moisture 12.45%, crude lipid 4.76%, crude protein 48.46%, ash 11.61%, crude fiber 2.32%, and carbohydrate 20.4%.

2.4. Stocking and rearing of fry

Immediate after the absorption of the yolk sac, the hatchlings were transferred to previously set 15 hapas for sex reversal treatment and each replication contained 500 individuals of Nile tilapia fry. Four different doses i.e., 50 mg, 60 mg, 70 mg, and 80 mg 17α-MT/kg feed were used in T1, T2, T3, and T4 respectively, and compared to a hormone free (0 mg 17α-MT/kg feed) control group Tc. Then they were reared for 28 days and fed five times a day (Table 1). After 28 days of hormone treatment, the fry was reared for a further 90 days and fed with normal hormone-free feed at the rate of 10%–5% of the body weight.

Table 1.

Feeding rate of fry during hormone treatment.

Days Feed amount (% of the total body weight)
1–7 40
8–14 30
15–21 25
22–28 20
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2.5. Monitoring water quality parameters and sampling of fish

The temperature, pH, dissolved oxygen, and ammonia were calculated, and documented at a 7-day interval by using an automated YSI Pro Plus Multiparameter Instrument (Brannum Lane, USA) and a commercial ammonia test kit (Model HI 3824, Japan) respectively. Fry were sampled at 7 days intervals during the 28 days hormone treatment period and at 15 days intervals during the 90-day rearing period to assess the weight, length, and survival rate. The sampling of fish was done in the morning. The weight and length of the fry were determined using an electric balance (CAMRY digital electrical balance, Model EK 3052, Bangladesh) and a plastic scale respectively.

2.6. Tools for analysis of growth parameters

Major growth parameters were calculated by following the mathematical description of Pechsiri and Yakupitiyage (2005) and Panase and Mengumphan (2015).

%Weightgain=Meanfinalweight−MeaninitialweightMeaninitialweight×100
SGR(%/day)=W2−W1T2−T1×100;

where, W1 = the initial body weight (g) at time T1 (day), W2 = the final body weight (g) at time T2 (day).

2.7. Aceto-carmine squash process for gonad

A standard aceto-carmine squash test was done according to Guerrero and Shelton (1974). The staining solution consists of 0.5 g of carmine in 100 ml of 45% acetic acid. The solution is simmered for 204 min and cooled down to the filter. For microscopic examination, a sample of gonad was put on a glass slide. Then the aceto-carmine solution was added to the sample. Gonad was then examined with a covering slip under Optika microscope (model B-383PL) with Optika Digital Camera (Model B9, Italy) at 10× magnification.

2.8. Histology of gonads

Standard histology procedure was followed according to Van-Dyk and Pieterse (2008). Gonads were collected from experimental Nile tilapia and preserved in fixative (10% buffered formalin). Nile tilapia gonad slides were viewed under an electron microscope using magnifications 10 and 40 and the best images were taken using photographic equipment attached to a microscope. Photographs were taken using an attached digital camera Optika camera (Model B9, Italy).

2.9. Data analysis

The mean values, standard deviation, P values, and graphical analysis were performed using SPSS v26 and “Microsoft Excel 2019” computer-based software in Windows 10 setup. Differences between means were justified by using Duncan's Multiple Range test (DMRT) and significance were established at P < 0.05.

3. Results

3.1. Water quality parameters

The observed water quality factors as presented in Table 2 in all treatment groups were reported to be appropriate for supporting the optimal culture of Nile tilapia.

Table 2.

Water quality parameters during the different periods of experiments.

Months Temperature (°C) pH Dissolved oxygen (mg/l) Ammonia (mg/l)
October 25.13 ± 2.29b 7.56 ± 0.17a 5.26 ± 0.19b 0.02 ± 0.01a
November 21.06 ± 0.80a 7.39 ± 0.26b 5.35 ± 0.25a 0.01 ± 0.00a
December 21.79 ± 1.62a 7.42 ± 0.36a 5.66 ± 0.11a 0.02 ± 0.00a
January 22.16 ± 2.03a 7.54 ± 0.37a 5.45 ± 0.20a 0.02 ± 0.01a
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The row with different superscripts indicates significant differences at P < 0.05; values are means ± SD.

3.2. Growth and survival during 28 days of hormone treatment

The highest weight (1194.3 ± 129.83 mg) was observed in T2 followed by 1126.3 ± 118.85 mg in T4, 1122.3 ± 113.14 mg in T3, 1014.3 ± 83.03 mg in T1, and the lowest reported as 897.3 ± 83.19 mg in TC (Table 3). After 28 days hormone treatment period, the highest length (43.29 ± 1 mm) was observed in T2 followed by 41.43 ± 1.46 mm in T3, 41.05 ± 0.51 mm in T4, 39.02 ± 1.26 mm in T1, and 38.88 ± 1.88 mm in TC (Table 3). The control group (TC) showed the maximum average survival rate of 90.73 ± 1.60% among all groups. The highest survival rate of 85.2 ± 1.31% was obtained in the T2 group treated with 60 mg/kg of hormone among the hormone treated groups. The survival rate of other treatment groups i.e., T1, T3, and T4 were 82.2 ± 1.25%, 81.87 ± 1.79%, and 79.93 ± 1.01% respectively (Table 3). The SGR (%) was found as descent in T2 (16.76 ± 0.40), where lowest in Tc (15.75 ± 0.32).

Table 3.

Growth parameters and survival rate of Nile tilapia after 28 days of treatment.

Parameters Tc T1 T2 T3 T4
Initial weight (mg) 10.89 ± 0.03a 10.88 ± 0.03a 10.88 ± 0.03a 10.87 ± 0.03ab 10.85 ± 0.00b
Final weight (mg) 897.3 ± 83.19b 1014.3 ± 83.03ab 1194.3 ± 129.83a 1122.3 ± 113.14a 1126.3 ± 118.85a
Specific growth rate % 15.75 ± 0.32b 16.19 ± 0.29ab 16.76 ± 0.40a 16.55 ± 0.38a 16.57 ± 0.39a
Average daily weight gain (mg) 31.66 ± 2.97b 35.84 ± 2.97ab 42.27 ± 4.64a 39.70 ± 4.04a 39.84 ± 4.24a
Weight gain (mg) 886.4 ± 83.18b 1003.4 ± 83.03ab 1183.4 ± 129.84a 1111.5 ± 113.17a 1115.5 ± 118.85a
% Weight gain 8144 ± 754.65b 9220 ± 762.86ab 10875 ± 1201.52a 10230 ± 1066.79a 10281 ± 1095.43a
Initial length (mm) 0.85 ± 0.01a 0.84 ± 0.01a 0.85 ± 0.02a 0.85 ± 0.02a 0.86 ± 0.01a
Final length (mm) 38.88 ± 1.88b 39.02 ± 1.26b 43.29±1a 41.43 ± 1.46ab 41.05 ± 0.51ab
Length gain (mm) 38.03 ± 1.87b 38.18 ± 1.27b 42.43 ± 1.01a 40.58 ± 1.48ab 40.19 ± 0.51ab
Average daily length gain (mm) 1.36 ± 0.07b 1.36 ± 0.05b 1.52 ± 0.04a 1.45 ± 0.05ab 1.44 ± 0.02ab
Survival rate (%) 90.73 ± 1.60a 82.2 ± 1.25c 85.2 ± 1.31b 81.87 ± 1.79c 79.93 ± 1.01c
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The column with different superscripts indicates significant differences at P < 0.05; values are means ± SD).

3.3. Growth and survival rate during 90 days of the rearing period

The growth parameters and survival rate were recorded every 15 days interval during 90 days of rearing. The highest weight value (14.62 ± 0.59 g) was observed in T2 followed by 12.30 ± 0.37 g in T4, 11.05 ± 0.25 g in T3, 10.10 ± 0.57 g in T1, and the lowest mean weight of 8.64 ± 0.38 g was observed in control group Tc (Table 4). The maximum mean length (92.18 ± 3.01 mm) was observed in T2, and the lowest mean length (70.17 ± 3.75 mm) was recorded in the control group (Tc). The mean lengths of 86.16 ± 3.01 mm, 83.69 ± 4.54 mm, and 79.50 ± 5.07 mm were observed in T4, T3, and T1 respectively (Table 4). The maximum survival rate (87.71 ± 1.03%) was observed in the control group (TC), but the minimum survival rate (79.71 ± 1.87%) was observed in T1. T2 showed the highest survival rate (84.10 ± 1.75%) in comparison to other hormone-treated groups and T3 and T4 groups showed survival rates of 81.62 ± 0.59% and 83.33 ± 0.59% respectively (Table 4). The highest value of SGR (%) occurred at (2.79 ± 0.08) in juveniles from T2.

Table 4.

Growth parameters and survival rate of Nile tilapia after 90 days of the rearing period.

Parameters Tc T1 T2 T3 T4
Initial Weight (g) 0.99 ± 0.08a 1.01 ± 0.08a 1.19 ± 0.13a 1.12 ± 0.11a 1.13 ± 0.12a
Final Weight (g) 8.64 ± 0.38e 10.10 ± 0.57d 14.62 ± 0.59a 11.05 ± 0.25c 12.30 ± 0.37b
Specific growth rate % 2.52 ± 0.08b 2.55 ± 0.07b 2.79 ± 0.08b 2.55 ± 0.10b 2.65 ± 0.08ab
Average daily weight gain (g) 0.09 ± 0.00e 0.10 ± 0.01d 0.15 ± 0.01a 0.11 ± 0.00c 0.12 ± 0.00b
Weight gain (g) 7.75 ± 0.33e 9.08 ± 0.53d 13.42 ± 0.47a 9.93 ± 0.17c 11.17 ± 0.27b
% Weight gain 866.8 ± 65.12b 898.2 ± 66.01b 1130.5 ± 94.18a 890.8 ± 88.31b 990.6 ± 82.78ab
Initial length (mm) 39.88 ± 1.88a 39.02 ± 1.26a 41.14 ± 1.05a 41.10 ± 1.72a 41.05 ± 0.51a
Final length (mm) 70.17 ± 3.75a 79.5 ± 5.07b 92.17 ± 3.01c 83.67 ± 4.54b 86.17 ± 3.01bc
Length gain (mm) 31.29 ± 4.71c 40.48 ± 5.33b 50.02 ± 2.12a 42.57 ± 3.75ab 45.12 ± 3.27ab
Average daily length gain (mm) 0.35 ± 0.05a 0.45 ± 0.06b 0.56 ± 0.02c 0.47 ± 0.04bc 0.50 ± 0.04bc
Survival rate (%) 87.71 ± 1.03a 79.71 ± 1.87c 84.10 ± 1.75b 81.62 ± 0.59bc 83.33 ± 0.59b
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The column with different superscripts indicates significant differences at P < 0.05; values are means ± SD.

3.4. Growth performance during the 118 days experiment

Growth performance of Nile tilapia, including final weight, specific growth rate (SGR), average daily weight gain (ADWG), weight gain (g), % weight gain, final length, length gain, average daily length gain (ADLG), and survival rate, showed significant differences between the control group and hormone treated groups, and among the different treatment groups with very few exceptions (Table 5). Again, maximum SGR (%) was reported in T2 as 2.79 ± 0.08.

Table 5.

Growth parameters and survival rate of Nile tilapia after 118 days of experiment (28 days of hormone treatment and 90 days of rearing period).

Parameters Tc T1 T2 T3 T4
Initial weight (g) 0.01 ± 0.00a 0.01 ± 0.00a 0.01 ± 0.00a 0.01 ± 0.00a 0.01 ± 0.00a
Final weight (g) 8.64 ± .38a 10.10 ± .57b 14.62 ± .59c 11.05 ± 0.25b 12.30 ± 0.37bc
Specific growth rate % 5.65 ± 0.04a 5.78 ± 0.05a 6.09 ± 0.03b 5.86 ± 0.02a 5.95 ± 0.03b
Average daily weight gain (g) 0.07 ± 0.00a 0.09 ± 0.00b 0.12 ± 0.01b 0.094 ± 0.00b 0.10 ± 0.00b
Weight gain (g) 8.63 ± 0.38a 10.09 ± 0.57b 14.61 ± 0.59c 11.04 ± 0.25b 12.29 ± 0.37bc
% Weight gain 78476 ± 3433.82a 91706 ± 5225.69b 132776 ± 5381.94c 100394 ± 2231.43b 111739 ± 3386.22bc
Initial length (mm) 0.85 ± 0.01a 0.84 ± 0.01a 0.85 ± 0.02a 0.85 ± 0.02a 0.86 ± 0.01a
Final length (mm) 70.17 ± 3.75a 79.5 ± 5.07b 92.17 ± 3.01c 83.67 ± 4.54b 86.17 ± 3.01bc
Length gain (mm) 69.31 ± 3.75a 78.66 ± 5.07b 91.32 ± 3.03c 82.81 ± 4.54b 85.31 ± 3.00bc
Average daily length gain (mm) 0.59 ± 0.03a 0.67 ± 0.04b 0.77 ± 0.03c 0.70 ± 0.04b 0.72 ± 0.03bc
Survival rate (%) 87.71 ± 1.03c 79.71 ± 1.87a 84.10 ± 1.75b 81.62 ± 0.59ab 83.33 ± 0.59b
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The column with different superscripts indicates significant differences at P < 0.05; values are means ± SD.

3.5. Masculinization of Nile tilapia

The highest number of male (94.44%) fish were obtained in the T2 group whereas the control group showed marginal as 47.22%. Other treatment groups i.e., T3, T4, and T1 showed 91.67%, 88.89%, and 86.11% male respectively (Figure 2).

Figure 2.

Figure 2

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Percentage of males and females in different treatment and control groups after 118 days of the experiment.

3.6. Correlation between hormone doses, and percentage of sex reversal and SGR

The correlation graphs between the percentage of SGR and hormonal dosage revealed r2 value of 0.52 while it was accounted as 0.71 for sex reversal (Figure 3 A and B). This refers that the rate of sex reversal increases as the dose of hormone is reduced, and a trend of better % of SGR is reported as the dose of hormone increases.

Figure 3.

Figure 3

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Correlation curves for sex reversal and % SGR against the dose of hormones.

3.7. Confirmatory squash test for masculinization

After 118 days, the sex of Nile tilapia was confirmed by the squash test of the gonad. Male was identified by their long smooth tubular shape and female was identified by the abundant round shape object in the tube of the gonad (Figure 4 A–D).

Figure 4.

Figure 4

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Gonads of O. niloticus stained with aceto-carmine after 118 days of the experiment. Male gonads were identified by their long smooth tube shape (A and B). Female gonads were identified by the presence of numerous round oocytes (C and D). Here, A and C represent control groups whereas B and D represent hormone received groups.

3.8. Histology of gonad for confirmation of masculinization

Histology of gonads were performed to identify sex after 118 days of treatment. Male Nile tilapia was confirmed by the presence of different spermatogenic cells i.e., spermatocytes (Sc), and spermatids (St) in the transverse section of gonads (Figure 5A and C). Female Nile tilapia was confirmed by round oocytes in various stages i.e., peri-nucleolar stage; nucleoli at the periphery of the nucleus (Pn), cortical alveolar stage (Ca) along with follicle cell (Fc) in the transverse section of gonads (Figure 5B and D).

Figure 5.

Figure 5

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Histology of the gonads of Nile tilapia with H&E staining. Transverse sections of male gonad after 118 days of the experimental period showing Sc = Spermatocyte and St = Spermatid (A and C) as well as female gonad showing Pn = Perinucleolar stage of oocytes, Ca = Cortical alveolar stage of oocytes and Fc = Follicle cell (B and D). Here, both A and B represent control groups as well as C and D represent hormone treated groups.

4. Discussion

The growth and development of fish are primarily influenced by the different water quality parameters (Enders and Boisclair, 2016). Temperatures between 20 and 36 °C have been described as tolerable for tilapia culture (El-Sayed and Kawanna, 2008), though better performance occurred between 25–27 °C (Nivelle et al., 2019). The temperature recorded in this experiment ranged from 21 C to 28 °C. The present experiment was conducted in the late autumn to the winter season and for this reason, a higher fluctuation of temperature happened. The DO of the water body is crucial for fish culture (Mengistu et al., 2020) and >5 ppm in water is considered a prerequisite to maintaining decent fish production. The pH is deemed a vital environmental force for the production of fish (Swain et al., 2020). The concentration of ammonia should be between 0.01 and 0.02 mg/L in culture ponds, otherwise, it would cause mass mortality (Bhatnagar and Devi, 2013; Bhatnagar and Singh, 2010). The better growth and survival rate of aquatic animals refers to the optimal range of water quality factors and the health status of reared water reservoirs (Kembenya and Ondiba, 2021; Paul et al., 2019). Therefore, recorded water quality parameters in the present experiment were within the threshold for Tilapia culture.

The 17α-methyltestosterone (17 MT) is one of the extensively used synthetic hormones added in fish feed to yield all-male tilapia fry (Karaket et al., 2021). Straus et al. (2013) suggested 9 mg 17 MT/kg fish daily administration for 28 successive days to produce higher monosex fry for the same species. Better growth performance and feed conversion ratio were acquired while using a 60 mg MT/Kg diet for 28 days (Al-Hakim et al., 2013; Mehrim et al., 2019). About 93.3% of males were successfully produced by feeding fish at 60 mg/kg 17 α-MT and their growth metrics were reported to be superior (Jensi et al., 2016). Research by Kef et al. (2012) reported better survival 94.4%, and growth performance after 28 days of the hormone treatment period. Jensi et al. (2016) testified the highest weight and length acquisition at the dose of 60 mg MT for the same species. Higher doses like 70 mg and 80 mg MT/Kg diet did not exhibit a significant difference in performing better growth and survival rate compared to 60 mg MT dose (Jensi et al., 2016; Vinarukwong et al., 2018). Reduced weight and length values were obtained at 80 mg MT dose compared to 60 mg MT for the same species (El-Greisy and El-Gamal, 2012). A value of highest survival rate as 84.10% (Jensi et al., 2016), 88% (Alcántar-Vázquez et al., 2015) and 80 % (Kefi and Kang'ombe, 2013) had been reported for O. niloticus treated with 60 mg MT/Kg diet. An account of 90–95% of males has been obtained with 60 mg MT/kg feed for 30 days (Olufemi Oluseun Ajiboye and Yakubu, 2015), while Zaki et al. (2021) reported 90% of male populations at the dose of 60 mg MT. These might be due to differences in environmental conditions or the use of different tilapia strains. The group where the highest dose, 80 mg MT was administered showed 88.89% males which was less than those groups which received 60 mg and 70 mg MT/kg feed and yield 94.44% and 91.67% males respectively. Again, El-Greisy and El-Gamal (2012) reported 95% male population after 75 days of rearing, while Zaki et al. (2021) obtained 90% sexual stability after 112 days of rearing.

Histology is treated as an excellent tool for identifying, quantifying, and monitoring gonadal development in fish (Feist et al., 2015; Figueiredo-Fernandes et al., 2006). Several research have been approached to identify fish sex by using histological observation (Alonso-Fernández et al., 2011; El-Greisy and El-Gamal, 2012; Vinarukwong et al., 2018). Female gonads in fish are characterized by the presence of rounded oocytes with cytoplasmic and vitellogenic mass (Hossain, 2021; Shoko et al., 2015). Squash preparation from Aceto-carmine is also treated as a good and rapid assay for sex identification in commercial hatcheries (Karaket et al., 2021; Kiriyakit, 2014; Srisakultiew, 2013).

The evidence from this investigation suggests that 60 mg 17α-MT per kg feed dose is the most efficacious dose to produce quality mono-sex male Nile tilapia (O. niloticus) and indicated that 17α-MT hormone enhances the growth performance of Nile tilapia. The highest number of males was obtained at 60 mg dose along with the highest weight and length. The findings of the present study confirmed that hormone-treated groups showed higher growth performance than control groups. Further experimental investigations are needed to estimate the withdrawal period of the 17α-MT hormone and its impact on the aquatic environment. The present investigation suggests that mono-sex Nile tilapia producers can use the dose (60 mg 17α-MT/kg feed) to produce quality mono-sex male Nile tilapia without compromising optimal growth and production.

Declarations

Author contribution statement

Baadruzzoha Sarker, Bipresh Das and Mohammad Amzad Hossain: Conceived and designed the experiments; Performed the experiments; Analyzed and interpreted the data; Wrote the paper.

Shawon Chakraborty: Performed the experiments; Wrote the paper.

M. M. Mahbub Alam and Mohammed Mahbub Iqbal: Conceived and designed the experiments; Performed the experiments; Analyzed and interpreted the data; Contributed reagents, materials, analysis tools or data; Wrote the paper.

Sohel Mian: Analyzed and interpreted the data; Contributed reagents, materials, analysis tools or data; Wrote the paper.

Funding statement

Mohammed Mahbub Iqbal was supported by Sylhet agricultural university research system (SAURES) and University Grants Commission (UGC), Bangladesh [SAURES201819FBG].

Data availability statement

Data will be made available on request.

Declaration of interest's statement

The authors declare no conflict of interest.

Additional information

No additional information is available for this paper.

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