Effects of liming and fertilization on zooplankton production and Clarias gariepinus fry reared in Hapas
One week old fry Clarias gariepinus (means weight 0.3±0.01 g) were cultured for 28 days in 1 m3 hapas suspended in earthen ponds. There were four treatments: T1, T2, T3 and T4 (control) with three replicates each. Lime [agricultural lime, Calcium hydroxide (CaOH)] (0.5, 0.15, 0.25 kg); inorganic fertilizer (NPK) 15:15:15 (1.5, 2.5, 3. 5kg) and organic fertilizer (poultry droppings) (0.5, 1.5, 2.5 kg) were used in the ponds to assess their effects on zooplankton production, pond productivity and C. gariepinus fry maturation. The fry were stocked at 20 fish/hapa and fed with artificial feed (coppens) at 5% of their body weight. Zooplankton analyses showed that miona were predominant (80 org/ml), copepods (71 org/ml), rotifers (76 org/ml), nauplii (67 org/ml and daphnia (79 org/ml). Mean growth rates of fry were: 4.2±0.23 g for ponds T1, T2 and T3 and 3.8±0.18 g for pond T4. Net primary productivity and nutrients in ponds showed that growth was significantly better in ponds limed and fertilized (T1, T2 and T3) (P>0.05). The present research recommends an application of lime and fertilizers at the above rates for effective production of fish foods.
Key Words: Lime, zooplankton, organic and inorganic fertilizers, floating net, Clarias gariepinus