Effects of different molasses application rates on planktonic composition in low salinity biofloc culture of Nile tilapia, Oreochromis niloticus fingerlings

This study aimed to evaluate the planktonic composition (phytoplankton, protozooplankton and zooplankton) in Oreochromis niloticus culture in low salinity (10 g L-1) biofloc with different molasses application rates. Fingerlings of Nile tilapia (3.15 +/- 0.5 g) were cultured for 70 days in a randomised design with two application rates: 30% and 50% molasses application of the total daily feed. Chlorella vulgaris was supplemented every 5 days (5 x 10(4) cells mL(-1)) and plankton samples were collected weekly. Evaluating planktonic data, diversity was considered low, and there was no significant difference (p < 0.05) between liquid molasses application rates. However, in the analysis of similarities, a difference was observed in relation to time. Cluster analysis identified two groups for phytoplankton and zooplankton. Chlorophyta group was the most abundant (>40%), with Chlorella genus being the main responsible for this dominance. In the zooplankton and protozooplankton communities, the genera with the highest abundance were: Anuraeopsis (42.60-76.96%) and Paramecium (70.15-81.25%), respectively. For zootechnical performance, the treatment with molasses application rates of 30% showed lower feed conversion ratio (2.06 +/- 0.17). The results suggest that there were significant changes in the plankton composition throughout the culture of Nile tilapia in the biofloc system, however, without any influence of the molasses application rates.

Automated summary

This study evaluated the planktonic composition in Oreochromis niloticus culture and found significant changes in composition throughout the culture, with no influence of molasses application rates.