Enrichment of <i>Artemia</i> With Synbiotic and Its Effects on Growth Nutrient Utilization Survival and Gut Microbial Communities of Larval Hybrid Catfish ( <i>Clarias microstomus</i>  ×  <i>Clarias gariepinus</i> )

<i>Artemia</i> (brine shrimp) is a vital live feed in aquaculture, providing essential nutrients during the early developmental stages of aquatic species. This study aimed to evaluate the efficacy of synbiotic-enriched <i>Artemia franciscana</i> as a live feed for hybrid catfish larvae (<i>Clarias microstomus</i> × <i>Clarias gariepinus</i>), using locally isolated probiotics (<i>Enterococcus faecium</i> and <i>Enterococcus faecalis</i>) and the commercial prebiotic inulin. The study was conducted in two phases. In Phase 1, <i>Artemia</i> were enriched for 6 h with four treatments: T1 (<i>E. faecium</i> W01 + inulin), T2 (<i>E. faecalis</i> + inulin), T3 (<i>E. faecium</i> W02 + inulin), and T4 (control and no synbiotics). Bacterial colonization was assessed microscopically and through colony counts at 2, 4, and 6 h post-enrichment. Synbiotic-treated groups (T1-T3) showed significantly higher bacterial retention than the control (T4), with T1 achieving the highest colonization levels (2 h: 6.98 log CFU/g; 4 h: 7.02 log CFU/g; 6 h: 7.10 log CFU/g; <i>p</i> < 0.05). Control values ranged from 5.12 to 5.45 log CFU/g. Microscopy revealed a distinctive red-brown gut coloration in treated <i>Artemia</i>, indicating successful colonization. In Phase 2, hybrid catfish larvae were fed enriched <i>Artemia</i> for 7 days, followed by a subsequent 7-day period transitioned to enriched <i>Artemia</i> and commercial pellet feed. T3 resulted in the highest weight gain (263.14 ± 34.70 mg), length gain (14.38 ± 5.10 mm), specific growth rate (SGR; 19.59 ± 1.17% day^-1), and the lowest feed conversion ratio (FCR; 0.10 ± 0.01), all significantly better than other treatments (<i>p</i> < 0.05). Although survival rates did not differ significantly, T3 recorded the highest survival (57.5 ± 3.81%). Forty presumptive lactic acid bacteria (LAB) were isolated from the fish gut, grouped into four main clusters. These results highlight the potential of synbiotic-enriched <i>Artemia</i> to enhance larval growth and gut health, offering an eco-friendly strategy to improve feed efficiency and reduce antibiotic dependance in aquaculture.