Predation dynamics of Rhodeus sinensis on Procambarus clarkii larvae: Behavioral patterns and aquatic plant refuge effects in crayfish aquaculture

Non-target fish are frequently present in crayfish aquaculture systems, yet limited research has explored their predatory impacts on crayfish larvae. To address this gap, three experiments were conducted to examine the predation dynamics of Rhodeus sinensis on Procambarus clarkii larvae, focusing on the effects of predator sizes, group sizes, and aquatic plant refuges. In experiment 1, Cox proportional hazards regression model revealed that P. clarkii larvae (8.40 mm and 11.30 mm) faced heightened predation risks from R. sinensis, particularly when the predator’s weight exceeded 2 g. Predation mortality significantly rose with increasing predator size. P. clarkii larvae primarily sought refuge in bottom corners and under heating rods, as indicated by Self-Organizing Map. Experiment 2, analyzed with Bayesian Additive Regression Tree, demonstrated that group predation of R. sinensis significantly enhanced predatory efficiency on larger crayfish larvae, resulting in reduced time to the first attack, increased total number of attacks and extended total attack duration. Experiment 3 disclosed that casualty and mortality rates of crayfish larvae markedly decreased when aquatic plants coverage exceeded 20 %, irrespective of plants types. Under predation pressure, crayfish larvae exhibited a preference for microhabitats on and under aquatic plants, indicating an adaptive behavior in response to predation. These findings underscore the susceptibility of P. clarkii larvae to predation by R. sinensis and suggest maintaining a 20 % aquatic plant coverage as an effective management strategy to mitigate predation risks and support juvenile crayfish survival in aquaculture systems.