Effect of light intensity on the growth of juveniles of Paralichthys orbignyanus sole (Valenciennes, 1839)

Author: Claudio Abdon Alvarez Verde  (Currículo Lattes)
Supervisor: Dr Marcelo Hideo Okamoto
Co-supervisor: Dr Luís André Nassr de Sampaio

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Many fish are visual predators and need an environment with minimal light intensity for their development and growth. On the other hand, very bright light can be stressful or even lethal. The aim of the present study was to evaluate the effect of light intensity on the growth of juveniles of the Paralichthys orbignyanus sole. Juveniles of 1.55 ± 0.03 g were randomly distributed in 12 50 L tanks (75 fish per tank) connected to a water recirculation system. The luminous intensities tested were 5 (5 ± 1 lux), 180 (176 ± 6 lux), 700 (712 ± 29 lux) and 2,000 lux (1,998 ± 64 lux), with three repetitions each. The fish were fed commercial feed six times a day, until they were apparently satisfied. The experiment lasted 42 days, and every two weeks,30 fish from each tank were measured and weighed. Throughout the experiment, the water in the tanks was maintained with 32 ± 1 salinity, temperature of 23 ± 1 ° C, dissolved oxygen of 6.6 ± 0.2 mg / L, pH of 7.8 ± 0.2 and ammonia total of 0.3 ± 0.1 mg / L. The photoperiod was maintained at 18 hours light and 6 hours dark. Growth data over time were analyzed with ANOVA (two-way), while the daily specific growth rate (TBI), apparent feed conversion (CAA), food intake (AI) and survival were analyzed with ANOVA (one way) with a 95% significance level, followed by the Tukey test, when significant differences were detected. At the end of the experiment, juveniles reared under 5 and 180 lux reached 10.1 ± 0.3 and 9.44 ± 0.3 g, respectively, higher weights than those reared under 700 lux (8.45 ± 0.3 g) and 2.000 lux (8.44 ± 0.3 g) (P <0.05). The TBI was greater in 5 lux (4.6 ± 0.2%) when compared to 700 lux (4.0 ± 0.1%) and 2000 lux (4.0 ± 0.1%) (P <0, 05), while the one obtained in 180 lux (4.3 ± 0.1%) did not differ from any treatment (P> 0.05). There was no significant difference (P> 0.05) in AAC at different light intensities, ranging from 1.04 ± 0.02 to 1.19 ± 0.03. The AI ​​varied between 1.53 ± 0.04 and 1.63 ± 0.03% / day and did not differ significantly (P> 0.05) in any treatment. Survival was 100% at all light intensities tested. It was observed that the growth of juveniles of sole is affected by the luminous intensity, and according to the results obtained in this work, its creation must be carried out between 5 and 180 lux.

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