Effect of different types of fertilizer on the growth of Sarotherodon galilieus (Linn. 1758) in earthen ponds
The cost of feed has been recognized as a major factor affecting the development and expansion of aquaculture in Nigeria. This is due to the fact that feed ingredients normally used for fish diets are seriously competed for by the livestock feed industry as well as for human consumption. The effect is that the potential for aquaculture and livestock development has not been realised. With increasing population, nonexpansion in aquaculture and livestock production results in a shortfall in protein intake requirement. It is against this background, that this study was carried out. Fertilizers are known to increase plankton production and consequently enhance fish yield. Some fish also feed directly on fertilizers that are organic manures. Fourteen (14) earthen ponds, each with an area of 25m² and depth of 1.0m were used for the study. Three types of fertilizers (N P K 15:15:15; super phosphate 0:20:0 and cattle manure) were used as treatments, with each of them at two concentration levels (high and low concentrations). Each of the resulting six treatments as well as the control was duplicated, giving a total 14 of ponds used in the study.
Sarotherodon galilieus was the study animal. Its growth in length and specific growth rate (SGR) was monitored fortnightly. The study lasted for 52 days. Results revealed that average fish length almost tripled, from a mean of 3.5 to 9.5 cm, while SGR ranged between 2.2 and 3.0% / day. N.P.K. fertilizers at the higher concentration of 0.7kg/25m²/2 weeks produced fish with the highest SGR of 3.0%/day, whereas ponds fertilized with cattle manure at the rate of 1.5 kg/25m²/2 weeks and the control produced fish with the lowest SGR values. From the results of this study, N.P.K. fertilizers are recommended for use in pond culture. There is, however, the need to determine the optimum concentration required for maximum efficiency.
Key words: Aquaculture, fertilizers, plankton, Sarotherodon galilieus, growth rate.