永兴岛及七连屿浅水礁区珊瑚礁鱼类多样性探讨

根据2005年~2013年对西沙群岛中永兴岛及七连屿浅水礁区珊瑚礁鱼类监控数据，利用分类学多样性指数、相对丰富度及相似性指数等对浅水礁区珊瑚礁鱼类种类组成及生物多样性进行研究。结果显示，永兴岛及七连屿浅水礁区珊瑚礁鱼类隶属于4目25科61属131种，科级多样性平均值为3.03，属多样性指数平均值为2.71，标准化的G-F指数平均值为0.13；鲈形目珊瑚礁鱼类种类及相对丰富度均占有绝对优势，永兴岛及七连屿浅水礁区珊瑚礁鱼类具种类较多、相似性较低特征，随着珊瑚礁环境质量下降、西沙群岛渔业活动的频繁以及超负荷的捕捞导致鱼类数量及密度减少，珊瑚礁鱼类密度呈下降趋势，平均鱼类密度从2005年的3.10尾/m2，下降到2013年1.23尾/m2，个体较小、游泳能力较强的礁栖鱼类更适合礁区生存，平均体长在6.00~10.00 cm。

Discussion of the diversity of the coral reef fish in the shallow reefs along the Yongxing and Qilianyu island

Based on the fish monitoring data of shallow reefs along the Yongxing and Qilianyu Island from 2005 to 2013, we have adopted taxonomic diversity index, relative abundance and similarity index to study the species composition and the biodiversity of the coral reef fishes.The result indicates that the coral reef fishes belong to 4 orders 25 families 61 genera and 131 species, with an average family diversity index of 3.03, genera diversity index of 2.71 and normalization G-F index of 0.13.The number of species and relative abundance of Perciformes outweigh all other orders.The coral reef fishes along the Yongxing and Qilianyu Island were characteristics of more species diversity but low similarity.Due to coral reef degradation, strong fishing activities and the overfishing, the density of coral fishes showed a downward trend from 3.10/m2 in 2005 to 1.23/m2 in 2013.Reef fishes with small individual size, str-onger swimming capacities and the body length at 6.00 cm to 10.00 cm is more suitable for the area.