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

ABSTRACT

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 × 10⁴ 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.

KEYWORDS:

• Phytoplankton
• zooplankton
• protozooplankton
• carbon source
• Chlorella vulgaris
• biofloc

Acknowledgements

The authors are grateful for the financial support provided by Coordination for the Improvement of Higher Education Personnel (CAPES) for the scholarships granted and National Council for Scientific and Technological Development-CNPq. We are also grateful to Dr. William Severi (Limnology Laboratory) for their contributions to this study. We thank the anonymous referees for their valuable suggestions.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Additional information

Funding

This work was supported by National Council for Scientific and Technological Development – CNPq [PQ 308063/2019-8, PQ309669/2021-9] and Coordination for the Improvement of Higher Education Personnel [process number 88882.436213/2019-01; 88882.436200/2019-01; 88887.497047/2020-00; 88887.663595/2022-00].

Notes on contributors

Priscilla Celes Maciel de Lima

Priscilla Celes Maciel de Lima earned a Bachelor’s degree in Fishing Engineering in 2015, a Master’s degree in Fishing Resources and Aquaculture in 2017 and a PhD in Fishing Resources and Aquaculture in 2022, all at UFRPE.

Rildo José Vasconcelos de Andrade

Rildo José Vasconcelos de Andrade earned a Bachelor’s degree in Fishing Engineering and then a Master’s in Fishing Resources and Aquaculture in 2020 both at the Universidade Federal Rural de Pernambuco-Brazil.

Allyne Elins Moreira da Silva

Allyne Elins Moreira da Silva earned a Bachelor’s degree in Fishing Engineering and then a Master’s in Fishing Resources and Aquaculture in 2020 both at the Universidade Federal Rural de Pernambuco-Brazil.

Clarissa Vilela Figueiredo da Silva Campos

Clarissa Vilela F. S. Campos is a PhD candidate in the Graduate Program in Fishing Resources and Aquaculture at the Universidade Federal Rural de Pernambuco (UFRPE), Brazil. She earned a Bachelor’s degree in Fishing Engineering in 2014 and a Master’s degree in Fishing Resources and Aquaculture in 2017, both at UFRPE.

Carlos Yure B. Oliveira

Carlos Yure B. Oliveira is a PhD candidate in the Graduate Program in Fishing Resources and Aquaculture at the Universidade Federal Rural de Pernambuco (UFRPE), Brazil, working on microalgae biotechnology. He earned Bachelor’s degree in Fishing Engineering in 2018 (also at the UFRPE) and Master’s degree in Aquaculture in 2020 at the Universidade Federal de Santa Catarina (UFSC).

Alfredo Olivera Gálvez

Alfredo Olivera Gálvez is a professor of Fishing Engineering at the Department of Fisheries and Aquaculture of the Universidade Federal Rural de Pernambuco (UFRPE). He earned a Bachelor’s degree in Biology at Universidad Ricardo Palma – Peru and then a doctorate in Biology of Aquatic Organisms and Aquaculture in 1998, at the Universidade Estadual Paulista Júlio de Mesquita Filho-Brazil.

Luis Otavio Brito

Luis Otavio Brito is a Professor of Fishing Engineering at the Department of Fisheries and Aquaculture of the Universidade Federal Rural de Pernambuco (UFRPE). He earned a Bachelor’s degree in Fishing Engineering and then a doctorate in Fishing Resources and Aquaculture in 2013, both at the Universidade Federal Rural de Pernambuco.