Stocking density-dependent growth and survival of nile nilapia (oreochromis niloticus) in cages at son fish farm, Buikwe district

Abstract

Both low volume high density cages and high-volume low-density cages are being used by most fish farmers to culture Nile tilapia (Oreochromis niloticus) on lakes, dams, rivers and earthen ponds. Choosing the most suitable cage type is one of the factors that lead to successful cage culturing of Nile tilapia. The study was conducted to determine the most suitable cage type when rearing Nile tilapia. Ten cages were selected for each cage category to determine the survival and specific growth rates of fish. LVHD cages were of dimensionsb2.5x2.5x2.5M stocked at stocking of l48fish/m3 made of a metallic frame and nylon nets and the HVLD cages were of dimensions 6x6x6M stocked at 78 flshlm3 made of plastic frame and nylon nets. The overall objective of the study was to provide information on the appropriate stocking density practices when rearing Nile tilapia in cages. Ten cages from each cage were selected at random - from cages being harvested and their survival and growth rates determined and also secondary data was collected from farm production records for the year 2017. The results of the study showed that HVIJD cages had a significantly higher (p<O.O5) specific growth rate (SOR) than LVII]) cages. There was no significant different (p>O.O5) in mean survival rate between the two cages categories. Physico-chemical water parameters on Lake Victoria at SON fish farm did not vary affects survival and growth rates of Nile tilapia since there within the suitable and safe ranges for their proper growth and survival in cages. The significant difference in mean specific growth rate of the two cage categories was clue to difference in levels of competition for food, space available for the fish as a result of difference in stocking densities. The mean survival did not show significant difference due to the fact that fish in both cage categories experienced uniform dissolved oxygen, pH and temperature since Physico-chemical parameters did not vary on Lake Victoria at SON fish farm during the study. The results of the study demonstrated that HVLD cages are the most suitable when rearing Nile tilapia fish because they had significantly higher specific growth rate and a slightly higher survival rate than LVHD cages.