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ABSTRACT
This study examines the buffering potency of calcium carbonate and oyster (Crassostrea gasar) shells on water acidity and its effect on the hatchability of fish eggs and survival of the fry of Clarias gariepinus. A concentration of 7.2g for five treatments; calcium carbonate(CACO3) [T1], unburnt uncrushed oyster shells (UUOS) [T2], burnt uncrushed oyster shells (UCOS) [T3] burnt crushed oyster shells (BCOS) [T4] burnt uncrushed oyster shells (BUOS) [T5] and the control (C). Eighteen 20-litre plastic bowls of three replicates/treatments used. C. gariepinus was spawned artificially and a measured quantity of the eggs and milt were stripped into each experimental bowl. pH, temperature, dissolved oxygen (DO), calcium, magnesium, sodium, potassium, phosphorus and total alkalinity were measured thrice weekly for four weeks at the initial and final stage after the introduction of shells into the water medium. This analysis was carried out using recommended procedures. Results obtained showed that the treatments containing shells increased the pH of the water as did the conventional calcium carbonate. T3 and T4 effected similar changes just as T1 (the conventional calcium carbonate) (7.87) in increasing the water pH to 7.43 at week 1 for T3 and 7.32 at week 1 for T4. Similar changes also effected across week 2 and 3 respectively. The percentage survived fry ranged from 28.33% in the control to 62% in T3. This was similar to the survival rate in T1 (55%) and T4 (50%) respectively.
At the final stage, pH ranged from 4.37±0.00 in the control to 7.87±0.06 in T1 week 1, temperature was from 28.33±0.5 to 30.00±1.00. Dissolved oxygen, from 4.67±0.25 in the control to 9.43±0.08 in T3, calcium ranged from 16.33±0.86 in the control to 78.77±0.18 in T1, magnesium ranged from 0.07±0.00 in the control to 1.95±0.07 in T4 and T5 respectively. The range of sodium and potassium was from 1.07±0.02 in T2 and 1.10±0.20 in T5 to 7.74±0.07 and4.50±0.3 in the control respectively. Phosphorus and total alkalinity varied from 0.09±0.01 in the control and 2.03±1.00 in T3 to 0.97±0.0 in T4 and16.33±0.58 in the control respectively.
