The effects of crowding stress on the growth, physiological response, and gene expression of the Nrf2-Keap1 signaling pathway in blunt snout bream (Megalobrama amblycephala) reared under in-pond raceway conditions

Effects of stocking density and dietary phosphorus levels on the growth performance, antioxidant capacity, and nitrogen and phosphorus emissions of juvenile blunt snout bream ( Megalobrama amblycephala )

“…GPx1 mRNA level was not influenced by phosphorus levels or their interaction, but high stocking density (60 fish/m 3 ) suppressed GPx1 mRNA level in the current experiment. The result agreed with a previous report by Yang et al (2019), who reported that GPx gene expression was reduced under the condition of high-density stress in blunt snout bream. This might be due to high density as a pressure factor, which led to the decrease in antioxidant capacity of this fish.…”

“…Nuclear factor erythroid 2-related factor 2 (Nrf2) has been shown to be a significant transcription factor that could regulate the gene transcription of antioxidant enzymes in mice (Muthusamy et al, 2012), and the Nrf2 signalling pathway could effectively improve the antioxidant property in fish (Feng et al, 2017). Oxidative stress caused by crowding pressure could be regulated by Nrf2 signalling pathway (Yang et al, 2019).…”

“…Nuclear factor erythroid 2‐related factor 2 (Nrf2) has been shown to be a significant transcription factor that could regulate the gene transcription of antioxidant enzymes in mice (Muthusamy et al., 2012), and the Nrf2 signalling pathway could effectively improve the antioxidant property in fish (Feng et al., 2017). Oxidative stress caused by crowding pressure could be regulated by Nrf2 signalling pathway (Yang et al., 2019). Moreover, high stocking density may lead to deterioration of water quality in a culture facility (Martin et al., 1998), and the discharge of aquaculture wastewater could lead to eutrophication of the receiving water (Shang et al., 1998).…”

“…The abovementioned differences may be related to the rearing environment and the composition of basic ingredients, which needs further research. Recent studies showed that high density could inhibit growth performance, cause oxidative stress (Yang et al., 2019) and increase nitrogen emissions of water in blunt snout bream (Yadata et al., 2020). A gap in knowledge still exists regarding the influences of stocking density and dietary phosphorus levels on nitrogen and phosphorus emissions in the water of this fish species.…”

Physiological effects of stocking density on the fishPiaractus mesopotamicusfed with red seaweed (Pyropia columbina) and β‐carotene‐supplemented diets

“…The TBARS levels decreased in the liver (basal and β‐carotene) and intestine (basal and seaweed) of fish exposed to crowding stress; meanwhile, increased levels were found in gills (basal and seaweed). Several authors reported augmented lipid peroxidation levels in fish tissues after high density‐exposure, indicating the occurrence of oxidative damage of cellular constituents (Andrade et al, ; Long et al, ; Yang et al, ). However, in agreement with our results, Liu, Zhu, Liu, and Ye () found decreased hepatic malondialdehyde (MDA) levels in Nile tilapia exposed to high stocking density with the addition of biofloc for 120 days, suggesting a reduction in the antioxidant capacity to cope stress.…”