Impact of stocking density on oxidative stress, digestive enzyme activity, ATPase function, and transcriptomic changes in juvenile Crimson snapper (Lutjanus erythropterus) during long-hour transportation

Abstract

Fish farms are often situated far from hatcheries, making the transport of fish larvae or juveniles from hatcheries to rearing farms a critical process. While optimal stocking densities for the transporting some marine species are established, there is limited information on the transportation of hatchery-produced juvenile Crimson snapper (Lutjanus erythropterus). This study aimed to assess how stocking density affects antioxidative stress, digestive enzymes, ATPases, and the transcriptome of Lutjanus erythropterus during long-hour transportation. The results revealed that water quality deteriorated as stocking density of Lutjanus erythropterus increased. At low to moderate stocking densities (20–60 g/L), L. erythropterus adapted environmental stress by boosting total antioxidant capacity, α-amylase activity, and ATPases activities. However, at stocking densities ≥ 80 g/L, significant oxidative stress occurred, with inhibition of antioxidant enzymes, α-amylase activity, and ATPases activities. Transciptomic analysis supported these biochemical findings, with KEGG enrichment revealing that differentially expressed genes were linked to anti-inflammatory and metabolic pathways, especially at high densities. In conclusion, 60 g/L is the optimum stocking density for L. erythropterus juveniles during road transport, while 80 g/L being a feasible but stressful alternative. These findings provide valuable insights for enhancing transportation practices to reduce stress on L. erythropterus juveniles in a cost-effective manner.