T. Mhango, R.E. Brummett-1997
Journal of the World Aquacuture Society, 28 (2) : 188-192 (from Current Contents)
Abstract:
Shire River tilapia Oreochromis shiranus broodfish were stocked at a density of 1.25 fish/m^2 and sex ratios of either 1:1 or 1:3 (males:females). Two weeks after stocking, fry collection began. Fry were then harvested weekly for 9 wk with a fine meshed dip net operated from the pond bank for 1.5 h each morning and afternoon. Ten weeks after fry collection began, all ponds were drained and completely harvested. Over the entire 84 d, fry production averaged 0.78 fry/m(2) per d and did not differ (P < 0.05) between treatments. Fry production per female was significantly higher (P < 0.02) in ponds stocked at a 1:1 sex ratio (111 fry/female) compared to a 1:3 sex ratio (66 fry/female). To avoid inbreeding without sacrificing production, a broodstock sex ratio of 1:1 can safely be used when producing O. shiranus fry at a density of 1.25 fish/m(2) in earthen ponds. Competition among females is a possible cause of reduced fry production in densely stocked brood ponds.
(Int Ctr Living Aquat Resources Management, POB 229, Zomba, Malawi)
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