TROPHIC NICHE AND SPATIAL VARIATION OF THREE DOMINANT SHRIMP SPECIES DURING THE EARLY PERIOD OF FISHING BAN IN THE YANGTZE RIVER ESTUARY

Shrimp play a crucial role as significant food sources in the Yangtze River estuary. This study focused on three dominant shrimp species: Exopalaemon annandalei, Palaemon gravieri, and Exopalaemon carinicauda, which collected from the southern and northern branches of the Yangtze River estuary in November 2022. Muscle samples were analyzed for δ¹³C and δ¹⁵N to calculate their trophic niche widths and overlaps, elucidating interspecies competition mechanisms and coexistence patterns, as well as their spatial differentiation characteristics from a nutritional ecology perspective. The research findings demonstrated that: (1) Among the three species, P. gravier exhibited a benthic feeding preference with the highest δ¹³C value (–17.05±3.23)‰, while E. annandalei leaned towards planktonic feeding with the lowest δ¹³C value (–20.19±1.50)‰. E. carinicauda, with larger individuals, had the highest δ¹⁵N value (10.28±0.55)‰. (2) There was a statistically significant difference (P<0.05) in δ¹³C and δ¹⁵N values between the southern and northern branches for E. annandalei, indicating spatial differences in its feeding habits and indirectly suggesting a relatively high environmental adaptability. (3) E. annandalei had the largest CR value (5.62), NR value (4.43), and SEAc value (3.07), implying it had the broadest basal food resources, more diverse nutritional levels, and higher resource utilization capacity compared to the other two species. (4) The ecological niche overlap between E. annandalei and the other two shrimp species was relatively small, showing a certain degree of ecological niche differentiation in terms of food resources. Conversely, P. gravier and E. carinicauda had a larger ecological niche overlap, suggesting they share similar food sources and experience intense dietary competition. However, feeding differences ensure interspecific coexistence. At the beginning of the current closure period, among the three dominant shrimp species in the Yangtze River estuary, E. annandalei is the most capable of occupying resources and has the best environmental adaptation in the estuary.