Growth and survival of hatchlings of Clarias gariepinus subjected to various pH
Paper Details
Growth and survival of hatchlings of Clarias gariepinus subjected to various pH
Abstract
The study was designed to evaluate the growth performance and survival of Clarias gariepinus hatchlings subjected to various pH treatments. The tests were conducted in plastic baths of 3.5 litre capacity filled to 2 litre mark with freshly prepared experimental solution and labelled according to pH requirements for the test. Each bath was stocked with forty hatchlings of body length of between 4.7 mm and 5.1 mm. They were exposed to the experimental solution for a period of four (4) days for growth estimation. For survival time, the test organisms were examined hourly for probable death. The hatchlings were not fed during the time of study, as their yolk at this stage of development still served as the only source of food. The length, measured as tip of the snout to tip of the caudal fin, was determined prior to stocking and daily, for the period. Every 24 hours the medium was checked for any change in pH and adjusted if any. The temperature of the culture media was constant (26.5oc) and dissolved oxygen content remained approximately 6.0mg/l. Average daily increase in length of between 0.3mm and 0.7mm was recorded in pH 4,5,6,7,8,9 and 10. There was no surviving hatchling on day 2 in pH 2,3,11 and 12 i.e. 100% mortality 24 hrs of stocking. Percentage mortality in the other pH varied between 75% (in PH 7) and 63.33% (in PH 4). Optimal growth and survival was recorded in PH 7 while the median lethal pH (ML50pH) is 4.25 and 10.10 for acidic and alkaline treatment respectively. The above result shows that reduced pH condition has a depressing effect on the growth rate of Clarias gariepinus hatchlings. This suggests the need for constant monitoring of pH changes in water especially where fish farming operations are practiced.
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