东海蟹类群落结构特征的研究

CRAB COMMUNITY STRUCTURE IN THE EAST CHINA SEA

依据1998年5月(春季)、8月(夏季)、11月(秋季)和1999年2月(冬季)在东海26°00′—33°00′N、127°00′E以西海域的蟹类资源调查资料,对东海蟹类群落结构的特征进行了定量分析。结果表明,东海蟹类优势种有双斑、银光梭子蟹、细点圆趾蟹、长手隆背蟹、日本、武士、锈斑、三疣梭子蟹、泥脚隆背蟹、锐刺长蟹和纤手梭子蟹。其中银光梭子蟹、细点圆趾蟹、双斑和三疣梭子蟹是东海蟹类的主要优势种。常见种是艾氏牛角蟹、红星梭子蟹、绵蟹、变态、光掌、十一刺栗壳蟹、七刺栗壳蟹、象牙长螯蟹、卷折馒头蟹、直额、武装筐形蟹和显著琼娜蟹。种类组成特征方面,冬、春季蟹类少数优势种的优势性明显,秋季优势度种间差异不明显。种类数比较:东海南部最多(57种),中部次之(45种),北部最少(仅37种);不同季节间,春季最多(57种),其次是夏季(53种),秋、冬季较少(仅49种);水深越深的水域,种类数越多。多样性比较:冬、春、秋3季,从北到南,蟹类多样性逐渐增高,且随着水深加深而增大;夏季不同,水深小于40m的浅海多样性指数最高。东海蟹类共可分为3个生态类群,即广温广盐生态类群、高温广盐生态类群和高温高盐生态类群。

Using 3 shrimp beam trawlers as the investigation boats, we sampled crabs in 115 stations in the East China Sea (26°00′—33°00′N; 120°00′—127°00′E) during 1998—1999. Total catch from each trawl was counted and identified to species in taxonomy. The species composition and community structure of the crabs were then studied mathematically. A total of 71 crab species were recorded. Index of relative importance (IRI) was used in this paper to determine the importance of species, and a species with IRI above 1000 were regarded as dominant species. According to this standard, there were 11 dominant species: Charybdis bimaculata, Portunus argentatus, Ovalipes punctus, Carcinoplax longimana, Charybdis japonica, Charybdis miles, Charybdis feriatus, Portunus trituberculatus, Carcinoplax vestita, Phalangipus hystri and Portunus gracilimanus. Among them, Portunus argentatus, Ovalipes punctus, Charybdis bimaculata and Portunus trituberculatus were major dominant species. The abundance of the dominant species was varied with seasons. For example, 4 were in May: Ovalipes punctus, Charybdis bimaculata, Portunus argentatus and Carcinoplax longimana, accounted for about 85% of the total catch or individuals. Among them, Ovalipes punctus showed a much higher IRI value (57607) than the others', covered 74.2% of the total catch. In August, there were 5 dominant species: Charybdis bimaculata, Portunus argentatus, Ovalipes punctus, Carcinoplax longimana, Charybdis japonica, 80.4% of the total catch and 90.2% of the total individuals. In November, the number of dominant species increased to 9: Charybdis bimaculata, Portunus trituberculatus, Portunus argentatus, Charybdis japonica, Portunus gracilimanus, Charybdis miles, Carcinoplax longimana, Charybdis feriatus, Carcinoplax vestita, occupying 81.2% and 91.2% of the total catch individuals, respectively. In February, the number reduced to 6: Charybdis bimaculata, Portunus argentatus, Charybdis miles, Ovalipes punctus, Charybdis feriatus, Phalangipus hystri, 81.8% and 89.9% respectively. Regarding the species composition, differences between dominant species were significant in spring, summer, and winter, but autumn. If define IRI value ranging from 100 to 1000 as common species, 12 were listed: Leptomithrax edwardsi, Portunus sanguinolentus, Dromia dehaani, Charybdis veriegata, C. truncate, C. riversandersoni, Lyreidus stenops, Arconia undecimspino, Randallia eburnean, Calappa lophos, Mursia armata and Jonas distincta. Species were distributed unevenly in the area, 57 species in the south, and 45 in the middle and 37 in the north. Despite the spatial change, the species abundance exhibited also seasonal variation. It peaked in spring to 57 species, gradually dropped in the following three months to 53 in summer, and 49 in autumn and winter. In addition, the species abundance went up with water deepening. The diversity of crab community in the East China Sea was indicated by 3 indices: Margalef index (d), Shannon-Wienner index (H′) and Pielou's evenness index (J). In the winter, spring, and autumn, the diversity was higher in the north than in the south. However, in summer, in both north and south both were higher than in the middle area. Again, the diversity also varied with water depth. In winter and spring, the diversity indices went up as water deepened. In summer, the diversity of inshore species reached the maximum above 40m of water depths, and it increased further when water depth exceeded 40m. In autumn, the diversity peaked at water depth ranging from 40m to 80m. It was concluded that the community structure and diversity of crabs exhibited remarkable spatial and temporal variations. Based on their adaptability to habitats, all recorded species of crabs were categorized into three ecological groups: eurythermic euryhaline group, temperate euryhaline group, and tropical halophile group.