Researchers from Pukyong National University, Sun Moon University, and the National Institute of Fisheries Science have published a scientific review examining the changes it brings to fish survival and growth rate, and thus their economic feasibility.
The study highlights the benefits of raising fish in biofloc systems in terms of growth, survival, health, and disease resistance.
Below we offer you a summary of the publication, and at the end of it you can find the link to the original publication.
The need for biofloc technology (BFT) in fish farming
In fish farming, the highest productivity is achieved with larger volumes of food, which results in an increase in the production of waste, generating environmental and economic costs.
Between 20 to 30% of the total nitrogen that enters aquaculture ponds remains in the biomass of the fish, the rest becomes a water pollutant, producing high levels of toxic substances such as ammonia and nitrites.
Biofloc is an environmentally sustainable technology that uses beneficial microorganisms to absorb ammonia and nitrites produced by aquatic organisms’ food waste, feces, and urine.
Survival rate and growth performance of fish
The useful microorganisms contained in the biofloc activate the digestive enzymes of fish and increase feed efficiency, thereby improving their growth performance.
Biofloc has a positive effect on the survival rate by improving fish immunity, and the study reports improvements in tilapia (Oreochromis niloticus), carp (Cyprinus carpio), catfish (Clarias gariepinus), goldfish (Carassius auratus) and grey mullet (Mugil cephalus); however, this varies depending on the carbon source used.
Hematological parameters
Biofloc can contribute to the improvement of fish health due to the activity of digestive enzymes and physiological activity, and the evaluation of hematological parameters can be a good indicator to confirm its efficacy.
The authors of the study present evidence of the hematological and biochemical parameters of the fish species reared in biofloc, noting that erythrocytes are the most abundant cellular components in the circulatory system of fish, and play important roles in gas exchange and in cell respiration.
Antioxidant responses
Antioxidant responses in fish are linked to the health status of the fish, and various types of antioxidant responses are required to control the complex immune system of fish.
The researchers cite scientific studies where biofloc increases antioxidant capacity in C. carpio, C. auratus, and suggest that antioxidant responses can be increased by bioactive substances such as chlorophyll, polyphenols, carotenes, taurine, polysaccharides, phytosterols, and vitamins present in the biofloc.
Immune responses
The effective microorganisms in the biofloc act as immunity and growth stimulating factors, and enhancement in fish immunity can have a mitigating effect against fatal pathogenic infections.
Biofloc carotenoids are known to perform several bioactive physiological functions, including stimulating the immune system of fish and providing essential nutrition.
The study collects the immunological responses of fish reared in biofloc.
Disease resistance
The bioactive substances in biofloc have unique antagonistic applications against pathogens, thereby suppressing disease outbreaks and enhancing the immunity of farmed fish.
Bacillus, the dominant bacterium in the biofloc, is an important probiotic in fish farming, as it increases disease resistance and fish immunity.
According to studies, biofloc has protective effects against various diseases caused by bacteria such as Vibrio harveyi, Aeromonas hydrophila, Edwardsiella tarda, and Streptococcus iniae, which cause great damage to fish farms.
The study collects evidence of pathogen challenges of fish species reared in biofloc systems.
Conclusions
The researchers conclude that biofloc-raised fish may contribute to productivity improvements in the fish farming industry due to improved growth and survival rates.
“Fish reared in biofloc show better physiological indicators and less stress compared to the control group,” they conclude.
They also indicate that fish reared in biofloc had the highest disease resistance in challenge tests with V. harveyi, A. hydrophila, E. tarda, and S. iniae.
“Several physiological effects and resistance conferred to diseases in fish reared in biofloc systems have been confirmed,” the researchers conclude.
The study was funded by the National Institute of Fisheries Science, Ministry of Oceans and Fisheries, Republic of Korea.
Reference (open access)
Yu, Young-Bin, Jae-Ho Choi, Ju-Hyeong Lee, A-Hyun Jo, Kyung Mi Lee, and Jun-Hwan Kim. 2023. “Biofloc Technology in Fish Aquaculture: A Review” Antioxidants 12, no. 2: 398. https://doi.org/10.3390/antiox12020398
