Jorge Velazco-VargasandSilvia MartÃnez-Llorens
A study was conducted to assess the effect of temperature on egg development in an attempt to improve hatching success and fry production in Oreochromis karongae. Temperature-dependent development rates and hatching period for fertilized eggs stripped from O. karongae,a mouth brooder, were determined in a recirculating system set up in a hatchery at the National Aquaculture Center, Domasi, Malawi. Three treatments namely; 25, 27 and 29 �?C, were replicated thrice in 2-L Macdonald type incubation jars stocked with 265 fertilized stage 1 eggs of O. karongae, at water flow rate of 0.15 L/s. There was a curvilinear relationship between temperature and egg development, which was best described by a logarithm regression function. Hatching period decreased with increase in incubation temperature. The shortest hatching period was 7.3 days, which was observed at the highest incubation temperature (29°C) while the longest hatching period was 14.7 days, observed at the lowest temperature (25°C). Hatchability and fry survival were higher at higher temperatures. The study has, for the first time, ably described O. karongaeegg development rates which suggest that increasing incubation temperature holds the potential to increase fry production, which is currently a bottleneck.
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