Effects of individual and combined salinity-alkalinity exposure on egg hatching, larval survival, and early growth of largemouth bass (Micropterus salmoides)

Abstract

To address freshwater scarcity and limited aquaculture space, the utilization of saline-alkaline waters has emerged as a promising solution for aquaculture. However, the tolerance of largemouth bass (Micropterus salmoides) to saline-alkaline exposure during early developmental stages remains unclear. Therefore, this study systematically evaluated the effects of single salinity (S0-S18, ppt), single alkalinity (A0-A40, mmol/L), and their combined exposure on egg hatching rate, larval survival, and early growth and development of largemouth bass. Single stress experiments indicated that the safe thresholds for salinity and alkalinity were 6 ppt and 15 mmol/L, respectively. The 96-h median lethal concentrations (LC₅₀) for larvae were 9.76 ppt and 26.79 mmol/L, respectively. Based on these safety thresholds, combined stress experiments revealed that hatching and larval survival rates in the S6-A15 (6 ppt -15 mmol/L), S6-A20 (6 ppt -20 mmol/L), and S8-A15 (8 ppt -15 mmol/L) groups were not significantly different from the control, while the other salinity-alkalinity combinations exhibited varying degrees of synergistic effects. Furthermore, yolk consumption and conversion rates in the S6-A15 and S6-A20 groups were similar to those of the control. Notably, the total body length of larvae in the S6-A15 group at 20 days post-hatching (22.1 ± 2.33 mm) was significantly (P < 0.05) greater than that in the freshwater group (17.4 ± 0.89 mm), indicating that a suitable saline-alkaline exposure could promote early development in largemouth bass. In summary, this study demonstrates a safe saline-alkaline combination (S6-A15) for the early developmental stage of largemouth bass, providing an important theoretical basis for healthy aquaculture and selective breeding in saline-alkaline waters.