Abstract
Over-population and stunted growth had been major challenges in the culture of tilapia. The use of synthetic androgen 17- α Methyl Testosterone (MT) was a breakthrough. However, its optimum level towards effective masculinization and growth is a concern. The aim of this research was to ascertain the optimum level of MT towards effective all-male population production and growth of Black-Chinned tilapia. In the present study, the effect of different dose rates of synthetic androgen 17-α Methyl Testosterone (MT) i.e., 0, 30, 60, and 120 mg of the hormone per kg of feed on sex, growth, and condition of Black-Chinned tilapia was evaluated. MT was administered orally by using powdered dry starter feed (Crude Protein 40 %) and Ethanol. The fry was fed for 30 days in the experimental tanks. At the end of the experiment, the sex ratios were determined by examining the operculum coloration as a means of sex identification. Growth performance was monitored by measuring and recording the morphometric characteristics. Bodyweight and total length of the fish on the start of feeding, end of feeding (one month sex reversal period), and two months after feeding were measured. The results of the present study showed that all MT receiving treatment showed a significantly higher male proportion than the control (0 mg MT/kg feed individuals). In all MT treatments groups, the control expects the 30 mg MT/kg in feed individuals’ deviate significantly from the normal 1:1 sex ratio (Chi-square analysis). The dose rate of 120 mg MT /kg feed resulted in the maximum male population (92.7%). Hence, for an effective high percentage of all-male population production in Black-Chinned tilapia, 120 mg MT /kg in feed is recommended. In terms of growth and condition factor, all the individual treatments, as well as the control, showed no significant difference. All the treated individuals showed similar condition factors during the pre and post-treatment, however, the individuals treated with 30 mg MT /kg feed exhibited better condition during the pre-treatment than the post-treatment period. Temperature, pH and dissolved oxygen recorded in this study were within the desirable limit for tilapia.
Highlights
Sarotherodom melanotheron (Black-Chinned tilapia) is one of the most important fish species identified for culture both in fresh and brackish water environment, for the developing and under-developed countries in West Africa [1]
The maximum male population of 92.70 % was obtained in fish fed 120 mg Methyl Testosterone (MT)/kg feed while the minimum male proportion of 39.3 % was recorded for fish fed 0 mg MT/kg feed
The results show that the condition factor of the fish during the treatment period was slightly higher for fish fed 30 mg MT/kg feed, 120 mg MT/kg feed and 0 mg MT/kg feed than the period after the treatment (Table 5)
Summary
Sarotherodom melanotheron (Black-Chinned tilapia) is one of the most important fish species identified for culture both in fresh and brackish water environment, for the developing and under-developed countries in West Africa [1]. It’s candidature is characterized by stress-free spawning, good growth, ability to feed at the lower portion of the food chain, Ofori-Danson and Kumi [2], feeding on cheap artificial feed, inhabitation of wild range of aquatic habitat Few of the setbacks in culturing tilapia is early maturation and uncontrolled reproduction, which often lead to overpopulation of the production system and stunted growth [5]. As a consequence of the afore-mentioned challenges most uncontrolled cultured populations of Black-Chinned tilapia lose their market value in weight and size
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