Influence of Photoperiod on Productive Gains and Immune Resistance During the Larval Stage of the Neotropical Fish <i>Trachelyopterus galeatus</i> (Linnaeus, 1766)

This study evaluated the effect of photoperiod as a productive strategy during the larviculture of the neotropical species Trachelyopterus galeatus . A total of 560 postlarvae, with an average total length and weight of 6.61 ± 0.33 mm and 2.36 ± 0.10 mg, respectively, were randomly assigned to seven photoperiod treatments, each four replicates: (0L:24D) 0 h light and 24 h dark; (4L:20D) 4 h light and 20 h dark; (8L:16D) 8 h light and 16 h dark; (12L:12D) 12 h light and 12 h dark; (16L:8D) 16 h light and 8 h dark; (20L:4D) 20 h light and 4 h dark; and (24L:0D) 24 h light and 0 h dark. Larvae were fed Artemia franciscana nauplii three times daily over a 30‐day experimental period. At the end of the trial, fish were measured and weighed to assess productive and zootechnical performance. To evaluate immune resistance, 20 individuals from each treatment were redistributed into four aquaria at a density of five fish L −1 and subjected to a sublethal infection. Fish were exposed by immersion in production water to 1.2 × 10 8 colony‐forming unit (CFU) L −1 of Aeromonas hydrophila for 96 h of observation. Data were tested for normality and homoscedasticity using the Shapiro–Wilk and Bartlett tests, respectively, followed by analysis of variance (ANOVA) and mean comparisons via Tukey’s test (5%) in BioEstat and PAST software. Results showed that shorter photoperiods (0L:24D, 4L:20D, and 8L:16D) promoted better growth performance and batch uniformity, as well as enhanced immune resistance when challenged with the pathogen. Therefore, strategic photoperiod control represents a viable tool to optimize the productive performance and immunity of T. galeatus in aquaculture.