Critical feeding window: Influence of delayed Artemia nauplii provision on Pyrrhulina brevis larviculture

This study aimed to evaluate the impact of delayed Artemia nauplii introduction on the larviculture of the Amazonian ornamental fish Pyrrhulina brevis. A completely randomized design with four treatments and four replicates was implemented. Larvae were subjected to varying delays in Artemia nauplii supply: 0 (no delay), 2, 4, and 6 days and were subsequently fed until the end of the 20-day experimental period. Growth performance, point-of-no-return (PNR), and intestinal and muscular histomorphometry were assessed at the end of the experiment. No differences in length, weight, or uniformity were observed between larvae with no delay and those with a 2-day delay in Artemia nauplii supply (p>0.05). However, total mortality occurred in larvae exposed to delays of 4 days or longer by the fifth day of experiment. Larvae without delay exhibited a survival rate of 86.25%, significantly higher than the 20% survival rate in those subjected to a 2-day delay (p<0.05). The PNR for P. brevis larvae was determined to be 2.69 days (9.69 days post-hatching). No differences were observed in intestinal or muscle histomorphometry among treatments (p>0.05). These findings highlight that delaying Artemia nauplii supply critically reduces the survival of P. brevis larvae, potentially compromising the viability of larviculture production.