Effects of saline and alkaline stresses on the survival, growth, and physiological responses in juvenile mandarin fish (Siniperca chuatsi)

Saline-alkaline water is widely distributed and abundant worldwide. It plays a critical role in the advancement of the aquaculture and the comprehensive utilization of saline-alkaline resources. The mandarin fish (Siniperca chuatsi), a freshwater species with high economic value, and has potential for cultivation in such environments. We evaluated its tolerance to acute salinity and alkalinity, and investigated the growth and physiological changes under chronic saline and alkaline stress. Initially, the effects of acute salinity and alkalinity were estimated on mandarin fish (4.33 ± 0.31 g), and found that the LC50 for 96 h of salinity and alkalinity was 13.91 ppt and 13.45 mmol/L, respectively. Subsequently, over a 60-day period, we measured the survival, growth performance, and physiological responses in mandarin fish (22.53 ± 0.60 g) reared in freshwater (FW, the control group), saline water (SW; fixed salinity of 5 ppt) and alkaline water (AW; carbonate alkalinity of 8 mmol/L). The results indicated that neither SW nor AW group adversely affected survival rates, and growth performance in SW group was significantly superior to the FW group. Additionally, compared to the FW group, the AW group had a lower hepatosomatic index, while the SW group exhibited significantly higher meat content. In terms of physiological responses, the AW group showed elevated V-H+-ATPase (VHA) activity, whereas the SW group had decreased prolactin (PRL) levels. Furthermore, the mitochondria-rich cells (MRCs) in mandarin fish underwent morphological adaptations to saline and alkaline stress, indicating their role in osmoregulation and acid-base balance. Our results suggested that the mandarin fish demonstrated good tolerance to both salinity and alkalinity, indicating suitability for breeding in low saline and alkaline water. This research contributes to a broader understanding of saline and alkaline tolerance in aquaculture species and provides theoretical support for the cultivation of mandarin fish in saline-alkaline water. Moreover, the results of this study suggested that saline-alkaline areas and agricultural irrigation water in the world could be successfully utilized for sustainable aquaculture.