Abstract: The Yangtze Estuary is one of the most important fishing grounds in China, providing favorable ecological conditions for the survival and reproduction of numerous aquatic organisms. Following the implementation of the Yangtze River fishing ban, populations of economically valuable species such as Leiocassis longirostris have begun to recover. In this study, L. longirostris specimens were collected in May 2024 from the Yangtze River Estuary. Stomach content microscopic examinations were conducted to analyze dietary composition and spatial variation. A total of 25 prey taxa were identified, dominated by crustaceans, with the zoeae of the Chinese mitten crab (Eriocheir sinensis) overwhelmingly predominant. Diet composition varied across size classes. Juveniles primarily consumed water fleas and E. sinensis zoeae. Subadults mainly fed on E. sinensis zoeae with some individuals beginning to prey on fish, while adults exhibited signs of cannibalism. There was distinct spatial heterogeneity in prey composition among sampling stations, largely influenced by benthic resource distribution and environmental factors. The diversified dietary structure of L. longirostris reflects its strong adaptability to environmental changes, and crustacean resources—especially E. sinensis—showed substantial recovery following the fishing ban. These findings provide essential baseline data and scientific insights for fisheries resource conservation and ecological management in the Yangtze River Estuary.

Key words: Leiocassis longirostris, microscopic examination, feeding habit analysis, dietary preference, Yangtze River Estuary