Ecological Stoichiometric Characteristics Of Fishery Catches From The Beibu Gulf

Fishery catches（such as fishes and invertebrates）play an important role in mediating biogeochemical cycles in coastal areas by storing carbon（C）,nitrogen（N）,and phosphorus（P）and other elements in their body tissues at theoretically homeostatic rates.To maintain homeostasis,the consumers need to be in balance with their resource supply or alter their stoichiometric traits in response to environmental change.However,the potential variations in elemental stoichiometry of marine fishes and invertebrates are poorly understood.Therefore,this study took the Beibu Gulf sea area as the research area,the ecological stoichiometric characteristics and influencing factors of fishery catches were studied systematically in this sea area,which can enrich the ecological stoichiometric data of coastal fish and invertebrates China,and can contribute to the development of marine biogeochemical cycles and provide scientific basis for the protection and management of fishery resources.The main results were as follows:（1）The variation ranged of C,N and P element contents in the fishery catches from the Beibu Gulf were 25.17%～58.34%,6.14%～14.92%and 0.26%～4.67%,respectively,and the variation ranged of C:N,C:P and N:P were 0.98～9.72,19.15～348.08 and 4.67～75.59.Among them,the content of P element in fishes and invertebrates changed the most,resulting in the change of C:P and N:P.The Ca content of fishes was significantly positively correlated with P content（P<0.01）,but the Ca content of invertebrates was not correlated with P content（P>0.05）.The C content of fishes and invertebrates was significantly negatively correlated withδ¹³C（P<0.01）.However,the N content of fishes was significantly positively correlated withδ¹³C,while it was significantly negatively correlated withδ¹³C in invertebrates（P<0.01）,which indicated that the variations of C content and N content in fishes and invertebrates due to different food sources.The ecological stoichiometry of carbon,nitrogen and phosphorus in fishes and invertebrates from the Beibu Gulf showed significant interspecies differences.The C,N,and P contents and ratios of different body types and different families of fish were significantly different（P<0.05）,and the taxonomic level of the family was the best predictor of fish ecological stoichiometry.Fishes and invertebrates did not maintain strict homeostasis,with stabler homeostasis in higher trophic levels.（2）The C,N,P contents and their ratios of the three dominant fish species（Saurida tumbil,Pennahia macrocephalus and Upeneus sulphureus）from the Beibu Gulf were significantly correlated with body length andδ¹³C,but not with water quality indicators,indicating that the changes in C,N,and P concentrations were caused by individual development and food sources.This study found significant intraspecies differences in the ecological stoichiometry of carbon,nitrogen,and phosphorus among the three fishes,which did not maintain a strict homeostasis,but exhibited temporal differences in C:N:P.（3）The relative content of elements in fishery catches from the Beibu Gulf was C>N>H>Ca>S>P>K>Fe>Zn>Cu,and the constant elements of fishes（C,N,P,S,H,Ca and K）were higher than invertebrates,trace elements（Fe,Zn and Cu）were lower than invertebrates.The concentration of elements in fish body changes greatly during individual development,which was mainly affected by factors such as body length,diet and fat contents,and there were species-specific differences in the bioaccumulation and composition of each element.There were large differences in body element content and significant niche differentiation among fishes and invertebrate taxa from the Beibu Gulf,and each biological level（trophic and taxonomic groups）had a unique element composition based on its function and morphological structure,but the element composition had a certain degree of flexibility（homeostasis）due to environmental conditions.