Effects of different LED light spectra on rainbow trout (Oncorhynchus mykiss): in vivo evaluation of the antioxidant status.

Rainbow trout (Oncorhynchus mykiss) farming is one of the major aquacultures in Turkey. Some conditions in fish farming can induce oxidative stress leading to the deterioration in properties such as appearance/color, texture, and flavor in fish meat. This situation may cause the consumer not to prefer edible fish. Although there are some studies on the impacts of light intensity on fish welfare, the changes in the antioxidant enzyme activities have not been elucidated. In the current study, it was intended to examine in rainbow trout how cultivating under different wavelengths affects the antioxidant enzymes and acetylcholine esterase (AChE) activity, because its activity is associated with oxidative stress, and also the determination of which light is suitable for fish welfare was aimed. Rainbow trout larvae were grown under four lights with different wavelengths: natural sunlight and incandescent long-wave (red light), medium-wave (green light), and short-wave (blue light) LED light. The experiment lasted for 64 days. Biochemical assays were carried on in the brain, gill, and liver of rainbow trout. Antioxidant enzymes and AChE activity, which play an important role in the central nervous system, were assayed. In gill tissues, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glucose 6 phosphate dehydrogenase (G6PD), glutathione reductase (GR), glutathione S-transferase (GST), and AChE activities increased under all three light wavelengths. In the liver, while activities of antioxidant enzymes and AChE decreased in red light, all of them increased in blue and green light. In the brain, GPx, GST, G6PD, and SOD activities were reduced but AChE activity did not alter under all three light sources. In conclusion, light sources with different spectral structures caused important changes in the activities of antioxidant enzymes in rainbow trout. On this basis, it may be thought that this may be a response to the changing redox status of a cell. Based on our results, blue light sources may be suggested for fish welfare in rainbow trout culture, and providing fish welfare by changing light sources can be easy and cheap in fish farming.

The effects of light sources with different spectral structures on ocular axial length in rainbow trout (Oncorhynchus mykiss).

Every day, we are acquiring more and more clues regarding the effects of different spectral structures (SS) of light on ocular axial length (OAL). As a step towards understanding this association, this study sought to characterise the effects of light sources of different SS on OAL in fish through comparisons with indoor daylight. The experimental design was completely randomised with 4 treatments and 2 replications. Three hundred and fifty two rainbow trout (Oncorhynchus mykiss) were housed in 8 tanks and fed for 71 days. Differences in the mean values of ocular elongation were determined at the end of the experiment. The daylight group was exposed to indoor daylight in the hatchery environment, the red group was exposed to long wavelength light (600-650 nm), the green group was exposed to mid-wavelength light (495-570 nm) and the blue group was exposed to short wavelength light (420-495 nm). The values of the OALs in fish grown under the same light intensity, but with light of different spectral characteristics, demonstrated significant differences (p < 0.05). The mean OAL in the daylight group was determined as 3.64 ± 0.40 mm, as 3.70 ± 0.35 mm in the red group, as 3.53 ± 0.34 mm in the green group and as 3.42 ± 0.29 mm in the blue group. The mean OAL in the blue group was significantly shorter compared to the red (p = 0.003) and the daylight groups (p = 0.02). When compared with the long wavelength light and indoor daylight, the effect of short wavelength light on OAL in fish was observed to be negative. Exposure to light with modified SS of in indoor environments may be effective in stopping ocular elongation.