Effect of Fertilization Frequency on the Productivity of Earthen Ponds Cultured with All-Male Oreochromis Niloticus (Nile Tilapia).

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This study was conducted to evaluate the frequency of fertilization effect on the productivity of earthen ponds cultured with all-male Oreochromis niloticus (Nile tilapia) at Tano-Odumasi between June to December, 2014 in Ashanti region of Ghana. The effect of manuring regime was assessed on the water qualities of pond (which included nutrients in the form of nitrates and phosphates), plankton production, fish monthly growth rate and yield as well as the microbial contamination of the ponds water, fish skin and muscles. There were three replications per treatment and each pond was stocked with 600 fingerlings of the average 10.3g. All the experimental ponds received the same total manure inputs (600 kg). Fertilization frequencies used were 50 kg and 100 kg on biweekly and monthly basis respectively. Bagging method of manuring and supplementary feeding (2% of fish wet body weight) were used throughout the experimental periods of 180 days. Samples were collected on monthly basis apart from the microbial data of the ponds water, fish skin muscles which were done once. The data gathered were analyzed using independent T-test of variance at 95 % confidence level. Results indicated that ponds that were fertilized biweekly intervals gave greater net yield (7898.4±110 kg/ha), specific growth rate (0.833% day -1) and individual fish yield (315.59 g) than once a month fertilized ponds net yield (6504±62.6 kg/ha), specific growth rate (0.797% day -1) and individual fish yield (269.64 g) respectively. All the physico-chemical parameters and nutrients of the ponds water did not differ significantly and remained in an acceptable range for Oreochromis niloticus culture except ammonia concentration which was high. At the end of the study, it was also revealed that ponds water, fish skin and muscles had been contaminated by coliform bacteria including Total coliform, Faecal coliform, Enterococci coliform and Faecal enterococci when analyses was done using Most Probable Number (MPN) method. Although no Salmonella was present prior treatment of the fish is required before consumption.
A thesis submitted to the Department of Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology,in partial fulfilment of the requirements for the award of Masters of Philosophy Degree in Limnology and Fisheries,