Ecological niches of three dominant fish species in south-central waters of Beibu Gulf

【Objective】The purpose of the study was to compare the elemental composition and the differences in multidimensional stoichiometric and carbon and nitrogen stable isotope trophic ecological niches of three dominant fish species in south-central Beibu Gulf, so as to systematically understand the relationships between the major dominant fish species in this area, and to provide reference basis for the sustainable development and utilization as well as the scientific management of the fishery resources in south-central Beibu Gulf. 【Method】Three dominant fish species(32 Saurida tumbil, 34 Pennahia macrocephalus and 33 Upeneus sulphureus) collected from the south-central Beibu Gulf in April 2022were used as study subjects. The contents of 20 elements(C, N, P, K, Ca, Na, Mg, Fe, Zn, Mn, Ti, Cr, Co, Ni, Cu, As, Ba, Cd, Pb and Sb) and stable carbon and nitrogen isotopes(δ¹³C and δ¹⁵N) of the fishes were measured. Comparative analysis of elemental composition of the three dominant fish species and intraspecific and interspecific differences in their ecological niches was carried out by plotting multidimensional stoichiometric ecological niche maps and carbon and nitrogen stable isotope trophic ecological niche maps. 【Result】Obvious interspecific and intraspecific differences in element contents and carbon and nitrogen stable isotope contents were found among the three dominant fish species in southcentral Beibu Gulf,with the ecological niche rankings in terms of hyper volume as P. macrocephalus(280.97)>S. tumbil(174.45)>U. sulphureus(98.30), and the ecological niche area ranked as S. tumbil(6.63)>U. sulphureus(4.00)>P. macrocephalus(2.46). There was a certain degree of interspecific and intraspecific ecological niche overlaps among these three dominant species. For example,the highest probability of interspecific ecological niche overlap existed between S. tumbil and P. macrocephalus(14.04%), while the lowest probability of interspecific niche overlap was between S. tumbil and U.sulphureus(1.76%). Meanwhile, the highest intraspecific ecological niche overlap was in U. sulphureus,followed by S.tumbil and P. macrocephalus.In addition, the multidimensional stoichiometric hyper volume ecological niche of the three dominant fish species was related to intraspecific variations, the larger the intraspecific differences, the greater the hyper volume niche. 【Conclusion】There are obvious interspecific and intraspecific differences in elemental content and carbon and nitrogen stable isotope content of the three dominant fish species in south-central Beibu Gulf. Both multidimensional stoichiometric ecological niche and carbon and nitrogen stable isotope trophic ecological niches can be used to characterize organisms' physiological traits and functions. However,compared with stable isotope trophic ecological niches, multidimensional stoichiometric ecological niches can better reflect the intraspecific differences. Thus, the interspecific and intraspecific differences of multidimensional stoichiometric ecological niches of organisms, including the ecological niche changes of fishery organism individuals at different developmental stages, will be explored in further studies, which can provide reference basis for the sustainable development and utilization as well as the scientific management of fishery resources.