Abstract
Synthetic androgens (male hormones) administered to fish nursery are being used in aquaculture to avoid sexual differentiation and unwanted spawning at the eggs or the first feeding fry stage of fish. Present trial was conducted with the aim to produce male common carp (Cyprinus carpio) by egg immersion technique. Through this little insight, the effect of different hormone concentrations (17α-methyltestosterone @ HC:150, 300, 450 and 600 µgl-1) with immersion times (IT: 24, 48 and 72 hrs) and their interaction effect (HC x IT) on the hatching percentage of Cyprinus carpio eggs, percent survival and percent of male's production was evaluated specifically. Results showed that egg hatching percentage decreased with increased IT likewise, survival of treated fry was affected by increasing the IT (P<0.001). The main interaction effect of HC x IT showed that the highest percent of male individuals (95%) was obtained at 450-600 µgl-1 HC for 72 hrs IT, followed by 88-92.50% at 150-300 µgl-1 HC for 72-hrsof IT, 87.50% at 48-hrs of IT for rest of the hormone treatments, and lowest 47.50% was recorded in control (P<0.05). Increased percent male of Cyprinus carpio was obtained with increasing HC across all ITs. It was observed that the immersion treatment at 600µgl-1 for 72 hours was more effective to change the sex ratio of pre hatch Cyprinus carpio. A comparative outlook made from this experimental trial that sex induction of Cyprinus carpio by eggs immersion using synthetic male steroid hormone is an alternative safe technique of fish sex reversal in contrast to oral administration of hormone in fish feed.
Highlights
In order to obtain significant results in breeding and growth in aquaculture industry, it is of crucial importance to choose suitable brood stock
Data analysis showed that hormone concentration (HC), immersion time (IT) and their interaction of both attributes (HC x immersion times (IT)) has significant effects on hatching percentage, survival percentage and masculinization ratio (P
58% was achieved in treatment at 150 μgl-1 hormone concentration for duration of 24 hours immersion time while lowest value for hatching percentage was recorded 37% at immersion time 48hrs for the concentration 450 μgl-1.Hatching percentages 50%, 41% and 39% were recorded for 300, 450 and 600 μgl-1 hormone concentrations, respectively when immersion time provided for 24hrs.While for immersion time of 48hrs, 52%, 46% and 37.50% and 37% eggs hatching percentage were recorded at 150, 300, 450 and 600 μgl-1 hormonal concentrations, respectively
Summary
In order to obtain significant results in breeding and growth in aquaculture industry, it is of crucial importance to choose suitable brood stock. Several tools and techniques has been used by fish cultivators to achieve the goals i.e. control of sexual differentiation in different ways for various fish species and to control the unwanted spawning in culturing ponds (Fernandino and Hattori, 2019), So the methods that increase the male population including manual sorting of sexes by visual examination, gene manipulation, sex reversal via steroid hormone and hybridization are under consideration (Dunham, 2011). Testosterone is a synthetic steroid hormone which is used to produce male fish and for better growth of fish for mono sex culture in aquaculture. It is species specific because sex determination is a complicated process for which each step may vary among populations. The success of mono-sex male population production on this drive has been achieved through sex reversal. 17α–methyltestosteronetreatments to fish are the most suited and reliable methods to attain sustainable fish stock (Megbowon & Mojekwu, 2014)
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