Journal of Aquaculture & Fisheries Category: Aquaculture Type: Research Article

The Growth and Survival of Various Forms Androgen Sex - Reversal Oreochromis niloticus Cultured Using Hapas in Concrete Tank

Omoike A1*, Falaye AE2, Okoye FC3 and Abubakar S3
1 Department Of Biological Sciences, Bells University Of Technology, Ota, Nigeria
2 Department Of Aquaculture And Fisheries Management, University Of Ibadan, Ibadan, Nigeria
3 National Institute For Freshwater Fisheries Research, New Bussa, Nigeria

*Corresponding Author(s):
Omoike A
Department Of Biological Sciences, Bells University Of Technology, Ota, Nigeria
Tel:+234 8062099220,
Email:dromoike@yahoo.com

Received Date: Feb 02, 2021
Accepted Date: Feb 08, 2021
Published Date: Feb 15, 2021

Abstract

The production of same sex Oreochromics niloticus to enhance better and uniform growth for Tilapia culture has called for technological means using sex-reversal hormones Methyl Testosterone (MT), this study will look into the percentage growth and survival of Oreochromics niloticus fry. The experimental fish Oreochromics niloticus fry of 0.90 cm total length were fed with three artificial feeds treated with three forms and concentrations of Methyl Testosterone (MT): Treatment A has 30mg/kg in tablet form, Treatment B was 30mg/kg in oil form and Treatment C was 50mg/kg in tablet form. A 35 days trial feeds were fed to the fish 5 times each day to obtain all male Tilapia fry population and grown to fingerling stage in outdoor tank for 56 days. The sex - reversal efficiency of the MT was analyzed after feeding the fry/fingerlings in hapas mounted inside outdoor tank. Conversion efficiency, condition factor and survival rate of the fry/fingerlings were also analyzed. The result obtained from the study shows that the sex reversal was effective in that the male: Female ratio was significantly different (p > 0.05) in favor of the male. The temperature had significant effect on the growth rates of the fingerlings, but showed no effect on their survival (p > 0.05). The food conversion ratio and condition factor did not show any significant difference (p > 0.05).  This study shows higher form of the tablet of MT seems to be more potent than the oily form, The highest average final weight was recorded in treatment B but the FCR shows no significant difference (p > 0.05) in the treatments, this study has revealed that the different form and concentration of Methyl Testosterone (MT), has potency for growth rate, sex reversal with high survival rate of Tilapia fry.

Keywords

Growth; Methyl testosterone; Oreochromis niloticus; survival; Sex reversal

INTRODUCTION

Among all the fish families in Nigeria, Tilapia is one of the cheapest sources of animal protein [1]. Megbowon and Mojekwu [2], said that Tilapia has become the second most important finfish in aquaculture after carps and because of their large size, rapid growth and palatability, the focus of most aquaculturist are on number of Tilapiine cichlids. The main species cultured in ponds, cages and pens is the Nile tilapia (Oreochromis niloticus). It is low in the food chain but generally has the problem of over-population due to the culture system especially in ponds. Jiménez-Badillo and Arredondo-Figueroa [3] reported that a major problem in commercial farms of tilapia species is their tendency to overpopulate ponds, for this reason all-male population of tilapia is desirable in grow-out ponds to eliminate or reduce reproduction. Among the methods developed to overcome the problem, hormonal sex reversal had been suggested as a possible solution and research in this area has received increased attention The problem with this fish is their early maturation and ability to breed every month [2]. This problem leads to stunted growth, which could be solved through monosex culture system. Monosex culture could be achieved by manual sexing, hybridization and hormonal sex - reversal. 

Hormonal sex - reversal is widely recognized as having significant advantage over both manual sexing and hybridization [4,5]. This technique involves the use of either androgen or estrogen treatment to over ride the androgenous sex determining mechanism in the developing embryo of fish and channel it to a male or female direction. According to Megbowon et al. [6], sex -reversal in tilapia, involves the treatment administration of male steroid to recently hatched fry so that the undifferentiated gonadal tissue of generic female develops testicular tissue, thus functioning reproductively as males. Hormonal control of reproduction by sex -reversal is gradually gaining ground in aquaculture in Nigeria, the most recent acceptable method in improving the productivity of cultured fish and its application is gaining high popularity in commercial fish farming practice. The objective of this study is therefore: To produce all - male Oreochromis niloticus fry through the administration of hormone, to compare the potency/efficiency of the two forms of the hormone, to determine the growth and survival of the fingerlings produced through the hormonal sex - reversal and to determine the percentage of the fingerlings that have been sex - reserved at the end of the study.

MATERIALS AND METHODS

Study area 

The study was carried out at the NIFFR’s hatchery complex, using both the indoor and outdoor facilities. 

The indoor system 

Six experimental flow-through plastic tanks of the indoor hatchery system were used for the first phase of this study which involves the application of the hormonal system to the Oreochromis niloticus fry. The plastic tanks were filled with water to a volume of 30 liters and covered with chicken - wire tray to prevent the treated fish from jumping out. The tanks were fitted with both inlet and outlet devices to maintain a simple flow - through system. The tanks were allocated to three treatments in two replicates under a completely randomized design. 

The outdoor system

An outdoor tank measuring 10 × 10 × 1.5 meters was used for the growth of the fry after the sex - inversion. A total of six net hapas of mosquito net mesh size with dimension of 1 × 1 × 1 meter were used and Kuralon rope was used to hold the hapas in a good position, about half - way submerged in water. 

Experimental fish 

Oreochromis niloticus breeders were collected from the Institute’s integrated poultry - cum fish culture system and stocked in a prepared nursery tanks measuring 5 × 5 × 1.0 meter. The 12 breeders were stocked in the ratio of one male to three females and fed with pelleted feed of 30% crude protein at 5% body weight, twice daily, morning and evening. 

After about three weeks, fry were observed in this nursery tank and were seined out of the tank and conditioned in a breeding through with adequate feeding and aeration for 24 hours. About 240 fry within the range of 9 mm to 11 mm total length were collected from the through, weighed and stocked in the flow - through tanks at the rate of 40 fry per tank. 

Preparation of the experimental diet 

The diets for the sex - inversion were prepared by alcohol evaporation method of Shelton et.al, [7]. The National Institute for Freshwater Fisheries Research (NIFFR) compounded pelleted feed of 30% crude protein level was used for this study. About one kg of the feed was ground in a mortar. Three forms of the androgen MT (tablet form, 30 mg/kg, oil form, 30 mg, kg/kg) were dissolved in 10ml of 10% solution of ethyl alcohol and each mixed with one kg of the ground feed. Each feed type was replicated. The thoroughly mixed feeds were oven dried at a temperature of 100°C for 6 hours. After oven - drying, the feeds were ground again into fine powder and packaged in plastic bags. 

The pelleted feed of 30% crude protein level used in feeding the fry in hapas in outdoor system was formulated using two ingredients, mix flour and blood meal under Peterson Square method. 

Experimental design and procedure 

The three treatments used for this study were: 

MT tablet at 30 mg/kg       -               A

MT oil form at 30 mg/kg   -               B

MT tablet at 50 mg/kg       -               C 

These were replicated, using six flows through tanks. About 40 fry were stocked in each tank after taking initial weight and total length. Subsequent measurements of weight and length were weekly. 

Feeding rates and feeding frequency 

The hormone - mixed feeds were fed to the fry at 10% body weight. The fry were fed 6 days in a week and 5 times daily at 7.00 am, 10.00 am, 1.00 pm, 4.00 pm and 7.00 pm. The weighed ration for the day was divided into 5 equal parts and each part fed to the fry at each feeding period by sprinkling the feed into a feeding ring at the centre of each tank. 

After 35 days the fry was transferred to the 6 net hapas in the outdoor concrete tank and fed with formulated pelleted feed of 30% c. p at 5% body weight, twice daily. These Frys were sampled fortnightly while mean weight, total length and survival rate were determined (Tables 1 & 2). 

Treatment

No stocked initial mean weight

Initial mean weight (g)

Final mean weight (g)

No Survived

% Survival

A1

40

0.011

0.148

27

67.5

B1

40

0.011

0.512

33

82.5

C1

40

0.011

0.180

28

70.0

A2

40

0.011

0.144

24

60.0

B2

40

0.011

0.400

35

87.5

C2

40

0.011

0.170

30

75.0

Total

40

0.065

1.554

177

442.5

Mean

40

0.011

0.259

29.5

73.75

Table 1: Feeding rates and feeding frequency 1. 

Treatment

No stocked initial mean weight

Initial mean weight (g)

Final mean weight (g)

No Survived

% Survival

A1

27

0.148

0.35

22

55

B1

33

0.512

1.349

32

80

C1

28

0.180

0.631

18

45

A2

24

0.144

0.38

17

42.5

B2

35

0.400

1.089

34

85

C2

30

0.170

0.542

28

70

Total

177

0.554

4.341

151

377.5

Mean

29.5

0.259

0.724

25.2

62.9

Table 2: Feeding rates and feeding frequency 2. 

Water quality parameter 

Water quality parameters monitored during the experimental period include; temperature, dissolved oxygen and pH. The temperature was measured with a laboratory hand thermometer calibrated from 0°C to 100°C. The dissolved oxygen was measured using the Winkler’s method while the pH was monitored using the Lovi - Bond comparator with Bomothymol as an indicator. 

Determinant of percentage male 

The percentages of male in the various treatments was obtained by viewing the genital papilla with the aid of hand lens and ink and by dissecting the fish if there is any doubt. 

The result obtained for the various parameters under test were subjected to analysis of variance to determine if either the treatment or their replicates had significant effect on the parameters. The chi-square test (x2) was used to determine the sex - reversal efficiency.

RESULTS AND DISCUSSION

Growth rate 

The fry in treatment B had the highest growth rate of 3.507mg/day followed by treatment C (3.446 mg/day) and lastly by treatment A (3.362 mg/day). The average length gained of the experimental fish in treatment B was 4.185 cm, followed by treatment C (3.025 cm) and lastly by treatment A (2.56 cm). The highest average final weight was recorded in treatment B (1.21g), followed by treatment C (0.58 g) and the least was treatment A (0.36 g). 

The analysis of the mean growth rate shows that there are no significant differences between the treatments and that the treatment had significant effect on the growth rate of the fish. This shows that the basal ingredient in the sex - reversal treatment had growth promoting effect on the fish. This was also observed by Lam [8] that androgen, estrogen and thyroid hormones, (growth hormones) are shown to have growth promoting effect in fish given in appropriate doses. As against the report of Jiménez-Badillo and Arredondo-Figueroa [3] who reported that the use of Androgen have no significant effect on growth. 

The best food conversion ratio of 1.68 was recorded in treatment B and the least (FCR) in treatment A (1.82). Analysis of variance of the FCR showed no significant difference in the treatments (p < 0.05). 

The highest condition factor was recorded in treatment C (0.965), followed by treatment B (0.905) and the least was treatment A (0.885). Analysis of variance of the condition factor showed no significant difference in the treatments (p < 0.05). 

Survival and male reversal ratio 

This survival rate observed after the 35days indoor and 56 days outdoor of trial demonstrate good survival ratio which agrees with the report of Jiménez-Badillo and Arredondo-Figueroa [3] that the hormone has no negative effects on the tilapia fry. The survival rate ranged from 60.0% to 87.5%. The mortality of the fry could be attributed to stress during sampling and cleaning of the experimental tanks. Despite this, the good survival ratio could be attributed to good water quality management and conducive physico - chemical conditions of the culture medium. 

The highest percentage of male was obtained in treatment C (98.5%), followed by treatment A (96.5%) and the least was treatment B (83.5%). This shows that the tablet form of MT seems to be more potent than the oil form and the higher the concentration of the tablet form, the more the potency. This agrees with the report of Jiménez-Badillo and Arredondo-Figueroa [3] who reported the effectiveness of the MT treatment at a dosage of 40 mg/kg of feed supply during 30 days to produce phenotypic males. Which also agrees with those of Kuwaye et al. [9], Ladu and Madara [10], who demonstrated the effectiveness of MT in other species. It is however advisable that cessation of the treatment of this hormone prior to marketing to reduce risk to consumers, according to Megbowon [11] who reported that sex reversing tilapia with MT does not lead to accumulation of the hormone in the fish flesh after cessation of hormone treatment. It was also reported by Johnstone et al. [12,13], that the hormone are not detectable after 100 hour of withdrawal of hormone treated diet. So farmers are safe to use this hormone but withdraw this hormone at least a month before sales of this sex reversed fish. 

The mean weekly record of some physico - chemical parameters (pH, DO and °C) shows that they are all within the tolerable range for the culture of Tilapia. The mean temperature ranged from 29° to 33°C. The DO ranged from 5 mg/l while pH was observed to be between 7.1 and 7.6.

SUMMARY AND CONCLUSION

Oreochromis niloticus fry were sex - reversed by oral administration of MT at the rates of 30 mg/kg and 50 mg/kg (tablet form) and 30 mg/kg (oil form) for 35 days in NIFFR indoor hatchery complex and allowed to grow to fingerling stage in outdoor tank for 56 days. 

Increase in length and weight were measured as well as percentage survival. In the end the percentage male was recorded by observing the genital papillae or dissection. 

The mean growth rate of fry treated with oil MT was the highest though it showed no significant difference to the fry treated with MT tablets. It can be said that the tablet MT is more potent than the oil MT.

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Citation: Omoike A, Falaye AE, Okoye FC, Abubakar S (2021) The Growth and Survival of Various Forms Androgen Sex - Reversal Oreochromis niloticus Cultured Using Hapas in Concrete Tank. J Aquac Fisheries 5: 036.

Copyright: © 2021  Omoike A, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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