Author(s): Umita Sah, Yuktilal Mukhiya, Suresh K Wagle

Abstract: Tilapia (Oreochromis niloticus) is a popular culture fish due to its economic importance. The basic problem of aquaculture however, is that a mixed sex, freely breeding Tilapia population reach sexual maturity early and start reproducing in grow-out ponds before they reach a marketable size, reducing the yield and value at harvest. Therefore, commercial production of Tilapia often relies on monosex culture of males. Growth evaluation of monosex and mixed sex is often required to convince farmers that the monosex culture is superior with respect to growth, yield and environmental concerns. Comparative growth experiment of mixed sex and MT hormone induced monosex Tilapia was conducted at RARS, Tarahara during August 2016 to January 2017 for a period of 150 days. Tilapia fry of monosex and mixed sex (mean weight 3.45±0.35 g) was stocked in respective triplicate hapas (3x2x1 m³ each) established in an earthen pond (0.2 ha). The stocking density maintained was 50 fish/m² for the first 90 days and later stocking density reduced to 10 fish/m². The stocked fish were fed with a pelleted ration containing 27% crude protein. The feeding rate was adjusted according the size of fish, 5% at the beginning to 3% at harvest. Water temperature (17-33 ^oC), dissolved oxygen (3.9-9.0 mg/L) and pH (7.2-8.6) all were within favorable range for fish culture. The growth of monosex Tilapia was significantly higher (p<0.05) compared to mixed sex Tilapia in all monthly growth check. Harvest weight of monosex and mixed sex Tilapia was 133.7 g and 101.5 g, respectively and the difference was significant (p<0.05). The size (length) of fish was also significantly larger (p, 0.05) for monosex compared to the mixed sex Tilapia. The relationship of fish lengths and weights expressed by power function revealed that the slope of the length weight regression lines was normal for monosex (2.94) and mixed sex Tilapia (2.84) with the high correlation coefficient (>0.9). The present findings indicated that monosex Tilapia had high growth rate with better shape and size over the mixed sex Tilapia.

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