Feeding habits and influencing factors of Coilia nasus in the main stream of the Huaihe River in Anhui, China.

Coilia nasus is one of the dominant fish species in the Huaihe River basin, with significant ecological and economic values. Research in feeding ecology is a great step towards deep understanding its life history. We analyzed stomach contents of 474 C. nasus samples collected in the main stream of the Huaihe River in Anhui in May and September of 2023, to investigate the composition of food, feeding intensity, feeding strategies, and the impact of environmental factors on food composition. Results showed that C. nasus in the main stream of the Huaihe River in Anhui primarily feed on 14 groups of prey organisms, such as decapods, copepods, and cladocerans. Exopalaemon modestus and Eucyclops sp. were the dominant prey. Individual weight, water temperature, turbidity, transparency, and water depth significantly affected feeding habits of C. nasus, and dissolved oxygen also had a significant impact. The empty stomach rate differed significantly between length groups, but not among seasons. The average stomach fullness index did not vary between length groups, but varied significantly among seasons. Our results indicated that C. nasus is a generalist predator primarily consuming animal-based prey, with intra-specific differences in food composition.