西沙群岛海域砗磲资源的调查

A survey of giant clams in the waters at Xisha Islands

砗磲是珊瑚岛礁的构成物种,对维护珊瑚礁生态系统平衡起着重要作用。近年来,由于非法捕捞和海洋生态环境影响,对我国西沙砗磲资源造成严重威胁。为掌握西沙海域砗磲资源现状,笔者于2017年6-7月采用截线样带法,对西沙主要岛礁海域砗磲的种类、分布及其与环境相关性进行了分析。结果显示,调查海域共发现4种砗磲:鳞砗磲(Tridacna squamosa)、长砗磲(T.maxima)、番红砗磲(T.crocea)和砗蚝(Hippopus hippopus),分别占总数的71.9%、15.6%、9.4%和3.1%。西沙不同岛礁海域砗磲密度、物种多样性指数存在显著差异,砗磲平均密度为0.026个·m^(−2)。砗磲密度与珊瑚覆盖率呈显著正相关(P<0.05,R^(2)=0.7065),表明珊瑚覆盖率是影响砗磲分布的重要因素。

Giant clams are the largest living marine bivalves inhabiting coral reefs,and perform a significant ecological role in maintaining the balance of coral reef ecosystem.In recent years,giant clams in the waters at Xisha Islands,China are seriously threatened due to overfishing and the deterioration of the marine environment in the coastal areas.In order to master the present status of giant clam resources at Xisha Islands,a survey of giant clams in the waters at the main islands of Xisha Islands were made by using the method of line intercept transect to determine the species and distribution of the giant clams at Xisha Islands in the South China Sea from June to July 2017,and then analyze the correlation of the giant clams with the environment in the waters at the main islands of Xisha Islands.The results showed that there were four species of the giant clams in the survey area,including Tridacna squamosa,Tridacna crocea,Tridacna maxima and Hippopus hippopus,accounting for 71.9%,15.6%,9.4%and 3.1%of the total giant clams,respectively.The giant clams in the waters of different main islands of Xisha Islands are significantly different in habitat density and species diversity index.The average density of the giant clams is 0.026 ind/m2.Correlation analysis showed that there was a significant positive correlation between habitat density and coral reef coverage(P<0.05,R2=0.7065).This shows that coral reef coverage is an important factor affecting the distribution of giant clams.This result can provide scientific basis for the conservation of giant clam resources in Xisha Islands in China.