Highlighting antibiotic-free aquaculture by using marine microbes as a sustainable method to suppress Vibrio and enhance the performance of brine shrimp (Artemia franciscana)

Brine shrimp nauplii are widely used as live food in fish and shellfish aquaculture but they may transmit pathogenic Vibrio to the target species causing significant economic loss. Heavy usage of antibiotics is expensive and environmentally damaging. Use of natural microbes as probiotics for disease management is a more sustainable strategy. In this study the abilities of four marine microbes-Debaryomyces hansenii, Ruegeria mobilis, Lactobacillus plantarum and Bacillus subtilis-to suppress Vibrio spp. and promote growth performance and survival of brine shrimp (Artemia franciscana) were investigated. Nauplii (Instar II) were exposed to 10⁸ CFU mL^-1 of one of the four microbes; a control without added microbes was included for comparison. The nauplii were fed daily with the microalga Nannochloropsis oculata. Population change, survival, weight gain, length gain, enzyme activity, microbial retention and body biochemical composition of the brine shrimp were measured. The results showed that B. subtilis and L. plantarum significantly decreased the body loading of Vibrio spp. in A. franciscana. Survival rate, weight gain and length gain of (A) franciscana all increased in L. plantarum and (B) subtilis treatments, but the growth performance in the D. hansenii and R. mobilis treatments was less consistent. Higher lipase and protease activities and lower body ash content in the brine shrimp were observed in the B. subtilis and L. plantarum treatments (P < 0.05). The abundance of B. subtilis in the brine shrimp was relatively stable even after 8 days of starvation. These findings demonstrate that B. subtilis was the most promising probiotic among the tested species, especially for long-term application without the need for repeated inoculation.