Temperature‐induced Effects on Ecdysis Frequency, Feeding, and Growth Response of Gazami ( Portunus trituberculatus ) Crablets

Gazami ( Portunus trituberculatus ) is a key species in stock enhancement programs in Japan. Recently, a severe decline in the Western Japan population has been observed, emphasizing the need for improvements in these programs. This study aimed to evaluate the effects of temperature on Gazami crablets under hatchery conditions, focusing on ecdysis frequency, inter‐ecdysis period (IEP), feeding behaviour and growth responses, to provide additional insights prior to their release into fishing grounds. Controlled rearing experiments were conducted in June 2023 and June 2024, under various temperature regimes. Crablets were reared in 100‐L tanks at 18°C, 22°C, 26°C, 30°C and 34°C, with a control group maintained at ambient temperatures (average: 19.79 ± 0.63°C in 2023 and 21.50 ± 0.73°C in 2024). Salinity was kept at approximately 33 ppt across all setups. The 26°C and 30°C treatments significantly improved growth performance compared to ambient and lower‐temperature treatments. The shortest IEP was observed at 30°C, positively influencing crablet rearing. However, at 34°C, ecdysis frequency significantly decreased, leading to slower growth and reduced food intake. These findings suggest that 30°C is optimal for enhancing ecdysis, feeding and growth in hatchery‐reared crablets. However, disparities between laboratory conditions and natural temperature variations should be considered when releasing juveniles into the wild. Understanding temperature's effects on Gazami crablets can help refine conservation and management strategies to support population recovery.