Evaluation of Growth Performance and Survival of Wild Collected Spotted Scat, Scatophagus argus(Linnaeus, 1766) during Rearing of Fry to Marketable Size Juveniles for Aquarium Trade at Varied Stocking Densities

Abstract

The spotted scat, Scatophagus argus has a good market as ornamental fish in smaller body size and wild seeds are available for further rearing to produce marketable size. Existence of no information on rearing of spotted scat fry in low saline brackishwater (<12 ppt) offered an opportunity to conduct an 8-week trial. Wild collected scat fry (0.33±0.04 g) was reared in indoor tanks (1000 L) at three densities (100, 200 and 300 numbers m^-3) and comparisons were made on the resultant growth, survival, length-weight relationship and condition factor data. Results on final length and weight exhibited better growth at the lowest density (P<0.05). Accordingly, growth rates decreased as density increased, exhibiting an inverse relationship (P<0.05, R²=0.88). Survival also decreased as density increased with differences among treatments (P<0.05). The function exponents showed that 200 numbers m stocking density produced fish with isometric growth (b=2.989; t=0.96; P>0.05) in good condition. The fish at 100 and 300 numbers m^-3 treatments had positive allometric and negative allometric growth, respectively indicating feeding and/or crowding problems. This study concludes that stocking density of 200 numbers m^-3 could be optimum to produce spotted scat with the best length-weight relationship, an average weight of 3.84±0.28 g and a survival of 87±3%. Although, fish produced at 100 numbers m^-3 stocking density had a better final weight (4.11±0.46 g), fish from 100 and 200 numbers m^-3 treatments will fetch similar price in the ornamental fish market as there was not a marked difference in growth. Therefore, the stocking density of 200 numbers m^-3 producing more numbers of healthy fish using same infrastructure is the most appropriate one from economic point of view and this system can be a viable option to the ornamental fish producers.