Effects of body size, temperature, and salinity on survival and growth of Oncorhynchus mykiss during salinity acclimation

This study investigated the individual and interactive effects of body size, water temperature, and ambient salinity on survival and weight gain of Oncorhynchus mykiss during salinity acclimation using a three-factor, three-level orthogonal design to identify optimal acclimation regimes. Nine experimental treatments were established across three body sizes (100, 250, and 500 g), three temperatures (10, 15, and 20 ℃), and three salinities (10, 20, and 30 ppt). Standard feeding protocols and daily tank maintenance were implemented across the entire 60-day experimental period. Survival rate and weight gain rate were calculated after cultivation, and all data were subjected to three -way ANOVA and range analysis. Salinity significantly affected fish survival, whereas body size and temperature did not. None of the three factors significantly affected weight gain. Range analysis revealed that salinity was the primary driver of variation in survival (R = 51.13), followed by temperature (R = 30.43) and body size (R = 1.50). By contrast, body size was the predominant factor governing weight gain (R = 30.40), with a much higher contribution than salinity (R = 3.10) and temperature (R = 2.40). Large-sized trout (500 g) reared at 10 ℃ and 10 ppt achieved the highest survival, and small-sized individuals (100 g) cultured at 10 ℃ and 20 ppt obtained maximum weight increment. A comprehensive evaluation of survival and growth performance demonstrated that the optimal domestication combination for survival was 500 g-15℃-10 ppt, which is particularly applicable to large O. mykiss is undergoing seawater transition. The optimal growth conditions are 100 g, 10 ℃, 20 ppt. This may be more suitable for juvenile growth-oriented cultivation. Our findings provide practical technical references for the domestication of O. mykiss in brackish and seawater and support the industrial advancement of its mariculture.