Probiotics and Prebiotics in Aquaculture
How beneficial microbes and the substrates that feed them improve fish and shrimp health, support water quality and help reduce antibiotic use, with mechanisms and application methods.
Overview
Probiotics are, by the FAO and WHO definition, live microorganisms that confer a health benefit on the host when administered in adequate amounts. In aquaculture they are used to improve the health of fish and shrimp, support water quality and reduce reliance on antibiotics. Prebiotics are non-living food ingredients that selectively feed beneficial microbes, and a combination of the two is called a synbiotic.
Common probiotics
Probiotics used in aquaculture include bacteria of the genera Bacillus, Lactobacillus, Enterococcus and Carnobacterium, the yeast Saccharomyces cerevisiae, and in some cases selected Pseudomonas and Vibrio strains. Bacillus species are widely used in shrimp culture and biofloc systems.
How they work
- Competitive exclusion — beneficial microbes compete with pathogens for space and nutrients and block their adhesion to the gut, limiting Vibrio and other pathogens.
- Antimicrobial production — secretion of inhibitory substances such as bacteriocins, organic acids and hydrogen peroxide that suppress pathogens.
- Improved digestion and nutrition — production of extracellular enzymes such as proteases, amylases and lipases.
- Immune stimulation — enhancing the host's innate immune response and disease resistance.
- Water-quality bioremediation — in ponds and biofloc systems, helping process waste and organic load.
Prebiotics and synbiotics
Prebiotics are substrates such as mannan-oligosaccharides (MOS), fructooligosaccharides and inulin that selectively nourish beneficial gut flora rather than pathogens. Synbiotics combine a probiotic with a prebiotic; for example, a Bacillus probiotic combined with a prebiotic oligosaccharide has been used to improve immune function in shrimp.
Application
Probiotics are delivered either mixed into the feed or added directly to the culture water, and are especially common in shrimp farming and biofloc systems. They are generally regarded as feed additives or water treatments rather than drugs, and offer a way to support health and reduce antibiotic use.
Evidence and limitations
Benefits are real but strain- and dose-specific: a product that works for one species, life stage or system may not work in another, and viability, storage and correct dosing all affect results. Regulatory status as feed additives varies by country. Probiotics complement, rather than replace, good husbandry, biosecurity and vaccination.