In order to investigate the effects of razor clams (Sinonovacula constricta) on the food composition and isotopic niches of swimming crabs (Portunus trituberculatus) and kuruma shrimp (Marsupenaeus japonicus) in polyculture systems, this study analyzed 60 P. trituberculatus, 60 M. japonicus and 30 S. constricta to quantify the food sources, food source contributions, and isotopic niches of cultured organisms using 18S rDNA barcoding and stable isotope techniques. The results were as follows: (1) In the P. trituberculatus-M. japonicus (PM) polyculture system, the Sobs and Shannon-Wiener indices of the stomach contents of P. trituberculatus and M. japonicus were not significantly different (P > 0.05). In the P. trituberculatus-M. japonicus-S. constricta polyculture (PMS) system, the Sobs and Shannon-Wiener indices of the stomach contents of P. trituberculatus and M. japonicus were also not significantly different (P > 0.05), but the Sobs indices of P. trituberculatus in the PMS system were significantly higher than those in the PM system (P < 0.05), M. japonicus shows a similar pattern. (2) 18S rDNA barcoding analysis showed the dominant taxa in the stomach contents of both P. trituberculatus and M. japonicus in the PM system were Trebouxiophyceae, Embryophyta and Rotifera, and the food overlap between them was 0.8992, which was significant (Q > 0.6). In the PMS system, the dominant taxa in the stomach contents of P. trituberculatus were Chrysophyceae, Intramacronucleata, and Embryophyta, and in M. japonicus were Chrysophyceae, Embryophyta, and Bacillariophyceae, in this system the food overlap was 0.2061, which was not significant (Q < 0.6). (3) Stable isotope analysis suggested, in both systems, the main food sources of P. trituberculatus and M. japonicus were iced trash fish, zooplankton, phytoplankton, and organic particulate matter (POM). Iced trash fish accounted 77.67% of food sources for P. trituberculatus and 69.42% for M. japonicus in the PM system, and 60.82% and 57.60% in the PMS system. (4) The isotopic niche overlap between P. trituberculatus and M. japonicus was 5.69% in the PM system and 1.21% in the PMS system. These results suggested food competition between P. trituberculatus and M. japonicus, and S. constricta can reduce the competition and isotopic niche overlap, improve the contribution of food sources such as phytoplankton. Razor clams also serve to purify the water and improve the utilization of iced trash fish by filtering phytoplankton (51.10%), POM (32.25%), SOM (7.47%), and iced trash fish (9.18%). Thus, P. trituberculatus-M. japonicus-S. constricta is a healthy and sustainable culture model.

为了研究蛏子的效果（缢蛏) 关于游泳蟹的食物成分和同位素生态位 (三疣梭子蟹) 和久留马虾 (日本金枪鱼) 在混养系统中，本研究分析了 60 P. 三结核菌, 60M. japonicus和 30S. constricta使用 18S rDNA 条形码和稳定同位素技术量化培养生物的食物来源、食物来源贡献和同位素生态位。结果如下： (1) 在三结核杆菌-M. japonicus(PM) 混养系统，胃内容物的 Sobs 和 Shannon-Wiener 指数三结核杆菌和M. japonicus没有显着差异（磷> 0.05)。在里面三结核杆菌-M. japonicus-S. constricta混养（PMS）系统，胃内容物的Sobs和Shannon-Wiener指数三结核杆菌和M. japonicus也没有显着差异（磷> 0.05)，但 Sobs 指数为三结核杆菌PMS 系统中的显着高于 PM 系统中的（磷< 0.05),M. japonicus显示出类似的模式。(2) 18S rDNA 条形码分析显示两者胃内容物中的优势类群三结核杆菌和M. japonicusPM 系统中的食物重叠率为 0.8992，具有显着性（Q > 0.6）。在 PMS 系统中，胃内容物中的优势类群三结核杆菌在M. japonicus分别为金藻科、胚藻科和芽孢杆菌科，在该系统中食物重叠为0.2061，不显着（Q < 0.6）。(3) 稳定同位素分析表明，在这两个系统中，主要食物来源三结核杆菌和M. japonicus是冰过的杂鱼、浮游动物、浮游植物和有机颗粒物（POM）。冰杂鱼占食物来源的77.67%三结核杆菌69.42%M. japonicus在 PM 系统中，在 PMS 系统中分别为 60.82% 和 57.60%。(4) 同位素生态位重叠三结核杆菌和M. japonicus在 PM 系统中为 5.69%，在 PMS 系统中为 1.21%。这些结果表明之间的食物竞争三结核杆菌和M. japonicus， 和S. constricta可以减少竞争和同位素生态位重叠，提高浮游植物等食物来源的贡献。蛏子还通过过滤浮游植物（51.10%）、POM（32.25%）、SOM（7.47%）和冰杂鱼（9.18%），起到净化水质和提高冰杂鱼利用率的作用。因此，三结核杆菌-M. japonicus-S. constricta是一种健康和可持续的文化模式。