The effect of stocking density on the growth and survival of improved and unimproved strains of Oreochromis shiranus

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Abstract

Growth performance and survival rate of improved strains (F<inf>5</inf> and F<inf>6</inf>) and unimproved strain of Oreochromis shiranus were assessed. Three stocking densities (5, 7 and 9fish/m<sup>3</sup>) were used to randomly allocate fingerlings, of mean weight 6±0.6g, into 27 hapas of 9m<sup>3</sup> each, fixed in a pond of 700m<sup>2</sup> at Bunda Fish Farm, Malawi. Stocking density significantly (P<0.05) affected the growth of the 3 strains though there was no significant difference between stocking density of 5 and 7fish/m<sup>3</sup>. The highest final weight was noted at a stocking density of 5fish/m<sup>3</sup> with an average weight of F<inf>6</inf> being 28.1g, followed by the F<inf>5</inf> (24.9g) and the unimproved (24.0g) strain. The improved strains had a higher final mean weight (F<inf>6</inf>: 23.41g, F<inf>5</inf>: 21.84g) than the unimproved strain (18.70g) but there was no significant difference between improved strains (P>0.05). The apparent genetic gain due to selection between the unimproved strain and F<inf>5</inf>, F<inf>6</inf> strains was estimated to be 16.8 and 25.2%, respectively. Based on this, farmers can be encouraged to use F<inf>6</inf> strain at a stocking density of 5fish/m<sup>3</sup>. The revelation that there was no difference between the improved strains has implications on the continuity of the selection program.

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M’balaka, M., Kassam, D., & Rusuwa, B. (2012). The effect of stocking density on the growth and survival of improved and unimproved strains of Oreochromis shiranus. Egyptian Journal of Aquatic Research, 38(3), 205–211. https://doi.org/10.1016/j.ejar.2012.12.013

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