山东半岛南部近岸海域蟹类群落结构特征

根据使用单船底拖网进行2014年8月和10月、2015年2月和5月4个航次的调查数据,对山东半岛南部近岸海域蟹类种类组成、时空分布、优势种、物种多样性等群落结构特征进行了研究。结果显示,4次调查共捕获蟹类15种,隶属于7科12属,其中三疣梭子蟹(Portunus trituberculatus)、日本蟳(Charybdis japonica)是主要经济种类,其余多为小型饵料型蟹类;双斑蟳(C.bimaculata)在4个季节中皆为优势种,三疣梭子蟹在8月和10月航次为优势种,优势种季节更替明显;生物量季节变化明显,春季时较低,在夏季达到峰值,夏季到冬季呈降低趋势;蟹类群落物种多样性指数(H′)变化范围为0.32~0.53,均匀度指数(J′)变化范围为0.23~0.37,丰富度指数(D)变化范围为0.32~0.55,其中物种多样性指数与丰富度指数季节变化明显,均匀度指数季节变化不明显;多元统计分析结果表明,山东半岛南部近岸海域4季节蟹类群落结构均可以划分为西南部海域组、东北部远岸海域组和西北部近岸海域组3个组群,季节间组群站位组成变化明显,群落结构不稳定。研究表明:1)山东半岛南部近岸海域蟹类以小型饵料型蟹类为主,蟹类多样性水平较低,优势种更替明显,蟹类群落不稳定;2)山东半岛南部近岸海域蟹类群落划分较为明显,特征种主要为双斑蟳、泥脚隆背蟹(Carcinoplax vestita)等小型饵料型蟹类。

Community structure of crabs in the coastal waters along the southern Shandong Peninsula

The coastal waters along the southern Shandong Peninsula waters are rich in fishery resources, and the spawning and feeding grounds for many important economic marine organisms are located here. In recent years, overfishing and pollution have caused considerable damage to fishery resources here, and crabs, including impor-tant economic species (such as Portunustrituber culatus and Charybdis japonica) and bait-type species (such as Charybdis bimaculata and Eucrate crenata) have been adversely affected. Although the community structure and diversity of crabs are of great significance for fishery production and fishery ecology, little research has been conducted in this respect in the southern Shandong Peninsula waters. Based on data from four bottom trawl sur-veys in this area from 2014 to 2015, the spatial and temporal distribution, structure community, dominant species, and diversity of crab populations were analyzed. Fifteen species of crabs were caught during the four surveys, which belonged to 7 families and 12 genera. The number of species caught changed seasonally because, as the area is located in the warm temperate zone, its temperature changes seasonally and the migratory crabs migrate to and from this area seasonally as well. Portunustritube rculatus and Charybdis japonica were the main economic spe-cies caught, and the others were low-value species. Because of the reduction in the number of natural enemies, the euryhaline Charybdis bimaculata was the dominant species in all four surveys. Biomass changed seasonally, with the highest biomass observed in summer and the lowest in winter. Except in autumn, distribution of biomass dif-fered regionally owing to the migration and foraging of C. bimaculata and P. trituberculatus. According to the data, the range of the Shannon-Wiener diversity index (H′) was 0.32–0.53, that of the Pielou evenness index (J′) was 0.23–0.37, and that of the Margalef richness index (D) was 0.32–0.55. The diversity index changed seasonally, indicating an unstable community structure and lower-level diversity of crab populations in this area. The diversity index was higher in the east, lower in the west, and higher in the near shore, and lower in the offshore; therefore, we conclude that the eastern offshore area along the southern Shandong Peninsula is suitable for crab growth. The results of a CLUSTER analysis showed that the crab species in every season in the coastal waters along the south-ern Shandong Peninsula could be divided into three groups: the southwestern waters group, the northeast waters group, and the northwest waters group. The populations in every group changed with season and the community structure was unstable. The key factor that influenced groups division was the presence of small bait-type species, such as C. bimaculata and Carcinoplax vestita, because the populations of the large economic species are facing considerable damage due to overfishing and environmental pollution. This study shows that: 1) Mostcrabs in the coastal waters along the southern Shandong Peninsula were small, bait-type species. The crab diversity was very low, and the dominant species varied considerably. 2) The community structure of crabs in the coastal waters along the southern Shandong Peninsula can be divided into three parts; most of the crabs found in this area are small bait-type crabs.