莱州湾4种大型甲壳类的空间与营养生态位

根据2010—2019年夏季莱州湾底拖网调查数据,研究了4种大型甲壳类(中国明对虾、三疣梭子蟹、日本蟳和口虾蛄)的优势度、种间联结、空间生态位特征,并应用碳氮稳定同位素数据分析了4种大型甲壳类的营养级、营养生态位与摄食来源。结果显示,口虾蛄、日本蟳是目前莱州湾夏季甲壳类最主要的优势种,放流种类中国明对虾、三疣梭子蟹为群落的重要种;4种大型甲壳类的种间联结性不强,显著正联结主要出现于中国明对虾与其他三者之间;日本蟳空间生态位宽度最高(2.45),口虾蛄(2.13)次之,中国明对虾(1.92)和三疣梭子蟹(1.93)较低;生态位重叠较高主要发生于中国明对虾与其他3种之间;4种大型甲壳类营养级相近(3.02～3.28),中国明对虾生态位总面积最大,三疣梭子蟹与日本蟳、口虾蛄的生态位总面积相近,三疣梭子蟹和日本蟳的营养生态位重叠较高;摄食来源分析表明,中国明对虾摄食双壳类比例更高,其他3种摄食来源同质化程度较高。目前莱州湾三疣梭子蟹和中国明对虾的优势度低于口虾蛄和日本蟳,表明增殖放流虽然扩大了三疣梭子蟹和中国明对虾的种群规模,但尚未较大程度改变甲壳类群落结构。综合4种甲壳类的群落地位、种间联结性、空间生态位宽度与重叠、营养级与营养生态位以及摄食来源的研究结果,中国明对虾与其他三者竞争相对较小,而三疣梭子蟹与日本蟳、口虾蛄竞争较大。为最大程度发挥增殖效益,建议在确定放流地点和放流数量时,应着重考虑相近生态位物种对放流物种的竞争和限制。

Niches of four large crustacean species in Laizhou Bay

Niche theory explains mechanisms of interspecific coexistence and competition in communities. Chinese shrimp (Fenneropenaeus chinensis), swimming crab (Portunus trituberculatus), Japanese stone crab (Charybdis japonica), and Japanese mantis shrimp (Oratosquilla oratoria) are all large-bodied commercially exploited crustacean species in Laizhou Bay, China, with similar food habits. Populations of two of these species, F. chinensis and P. trituberculatus, are also regionally enhanced. Study of the community status, interspecific associations, and spatial niche characteristics of these four crustacean species is warranted to guide stock enhancement and fishing quota management. Data for analysis of community status and spatial niche were collected by bottom-trawl surveys at 20 stations in summer from 2010 to 2019. Representative samples of these four crustacean species, and their potential food sources were collected in 2010, 2011, 2018 and 2019. Using stable carbon and nitrogen isotopes we analyze trophic levels, nutritional niches, and diets of these crustaceans. Average F. chinensis biomass (51.0 g/h) was lowest, followed by P. trituberculatus (107.0 g/h). In most years, O. oratoria and C. japonica were most dominant, and F. chinensis and P. trituberculatus were typically important species in the community. Associations between these four species are not strong, with a significant positive association occurring mainly between F. chinensis and the other three species. The niche width of C. japonica is greatest (2.45), followed by O. oratoria (2.13), F. chinensis (1.92), and P. trituberculatus (1.93). A high niche overlap is apparent between F. chinensis and the other three species; trophic levels of each are similar, ranging 3.02-3.28. The total niche area of F. chinensis is the greatest, while that of P. trituberculatus is similar to those of C. japonica and O. oratoria. Nutritional niche overlaps between P. trituberculatus and C. japonica are relatively high. Proportionally more bivalves are ingested by F. chinensis than any of the other species, for which diets are more homogeneous. Although populations of P. trituberculatus and F. chinensis have expanded through enhancement, the crustacean community structure in Laizhou Bay has not changed greatly. On the basis of community status, inter-species connectivity, spatial niche width and overlap, trophic level and nutritional niche, and the diets of these four crustaceans, F. chinensis is least competitive with other taxa, and P. trituberculatus is more competitive with C. japonica and O. oratoria. To maximize benefits of regional crustacean enhancement, we suggest consideration be given to competition between species, and niche similarities, to determine appropriate release sites and quantities.