FOOD RESOURCE PREDICTABILITY AND PREDATION STRESS ON GROWTH AND SURVIVAL OF JUVENILE SPINIBARBUS SINENSIS

To investigate the effects of food resource predictability and predation stress on fish growth and survival, as well as the underlying physiological and behavioral mechanisms, juvenile qingbo (Spinibarbus sinensis) were subjected to a two-factor experimental design involving food resource predictability (fixed vs. random feeding schedules) and predation stress (with or without visual predator cues). Four treatment groups were established and reared for 60 days. At the end of the growth experiment, standard metabolic rate (SMR), behavioral traits, biochemical parameters, and antipredator survival were assessed. Compared with the predictable food group, fish in the unpredictable food group exhibited significantly higher specific growth rate, weight gain rate, and feed efficiency, but significantly lower feeding rate and superoxide dismutase (SOD) activity, accompanied by significantly elevated plasma cortisol levels. Predation stress significantly inhibited growth and risk-taking behavior and reduced antipredator survival. In addition, predation stress significantly increased SMR only in fish exposed to unpredictable food resources. These findings suggest that although unpredictable food resources were perceived as an environmental stressor by qingbo, the fish were still able to promote growth by adjusting their energy allocation strategy. In contrast, predation stress likely diverted more energy toward maintaining vigilance and stress responses, ultimately suppressing growth and reducing subsequent survival. Furthermore, the uncertainty in food availability may exacerbate the negative effects of predation stress on individual fish.