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<p>A 28-day study was conducted to examine the effects of photoperiods with multiple light/dark cycles on growth performance and oxidative stress for largemouth bass (<i>Micropterus salmoides</i>) larvae in recirculating aquaculture systems (RAS). Larvae fish were exposed to four different photoperiods [light/dark (L:D), h] as follows: 6L:18D; 12L:12D; 18L:6D and 24L:0D. The feeding number was 8 times a day. The light duration of each treatment was 45&#xa0;min, 90&#xa0;min, 135&#xa0;min and 180&#xa0;min respectively in one light/dark cycle (feeding interval) of 180&#xa0;min. A total of six thousand fish (0.5229 ± 0.0180&#xa0;cm, 0.0021 ± 0.0002&#xa0;g) were randomly kept in the 12 cages (4 treatments × 3 replicates × 500 individuals). The results showed that the body weight, weight gain rate (WGR), specific growth rate (SGR), thermal growth coefficient (TGC), Fulton's condition factor (K) and mRNA expressions of growth hormone (<i>gh</i>) and insulin-like growth factor 1 (<i>igf-1</i>) generally increased with the extension of photoperiods, and they were highest in the 24L:0D treatment and were second in the 18L:6D treatment. The variation coefficients for body length (CV<sub>fl</sub>) and body weight (CV<sub>fw</sub>) were lowest in 18L:6D treatment. There was no significant difference in survival rate (SR) among four treatments. The levels of Malonaldehyde (MDA), total antioxidant capacity (T-AOC) and mRNA expressions of heat shock protein 70 (<i>hsp70</i>), corticotropin-releasing factor receptor 1 (<i>crfr</i><sub><i>1</i></sub>) and caspase-3 (<i>cas-3</i>) were all significantly higher in 6L:18D and 24L:0D treatments than those of 18L:6D and 12L:12D treatments. This indicated the photoperiods of 6L:18D and 24L:0D regimes induced an oxidative stress response in the larvae when the photoperiods were excessively compressed and extended. Overall, 18L:6D treatment is the optimal light regime for largemouth bass larvae culture in RAS. However, experimental comparisons between cyclic light/dark and continuous regimes are warranted to further evaluate animal welfare implications and inform aquaculture practice.</p>

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The photoperiods with multiple light/dark cycles affect growth and relate to oxidative-stress for largemouth bass (Micropterus salmoides) larvae in recirculating aquaculture systems

  • 期刊论文

  • 发表日期：

    2026年7月1日

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  • Yu-Hua Zhao,
  • Ping Wang,
  • Qi You,
  • Hou-Xiong He,
  • Xin-Yong Zhou,
  • Xiao-Juan Cao,
  • Jian Gao

摘要

A 28-day study was conducted to examine the effects of photoperiods with multiple light/dark cycles on growth performance and oxidative stress for largemouth bass (Micropterus salmoides) larvae in recirculating aquaculture systems (RAS). Larvae fish were exposed to four different photoperiods [light/dark (L:D), h] as follows: 6L:18D; 12L:12D; 18L:6D and 24L:0D. The feeding number was 8 times a day. The light duration of each treatment was 45 min, 90 min, 135 min and 180 min respectively in one light/dark cycle (feeding interval) of 180 min. A total of six thousand fish (0.5229 ± 0.0180 cm, 0.0021 ± 0.0002 g) were randomly kept in the 12 cages (4 treatments × 3 replicates × 500 individuals). The results showed that the body weight, weight gain rate (WGR), specific growth rate (SGR), thermal growth coefficient (TGC), Fulton's condition factor (K) and mRNA expressions of growth hormone (gh) and insulin-like growth factor 1 (igf-1) generally increased with the extension of photoperiods, and they were highest in the 24L:0D treatment and were second in the 18L:6D treatment. The variation coefficients for body length (CVfl) and body weight (CVfw) were lowest in 18L:6D treatment. There was no significant difference in survival rate (SR) among four treatments. The levels of Malonaldehyde (MDA), total antioxidant capacity (T-AOC) and mRNA expressions of heat shock protein 70 (hsp70), corticotropin-releasing factor receptor 1 (crfr1) and caspase-3 (cas-3) were all significantly higher in 6L:18D and 24L:0D treatments than those of 18L:6D and 12L:12D treatments. This indicated the photoperiods of 6L:18D and 24L:0D regimes induced an oxidative stress response in the larvae when the photoperiods were excessively compressed and extended. Overall, 18L:6D treatment is the optimal light regime for largemouth bass larvae culture in RAS. However, experimental comparisons between cyclic light/dark and continuous regimes are warranted to further evaluate animal welfare implications and inform aquaculture practice.