南沙群岛西南部和北部湾口海域鱼类物种多样性

Fish diversity in southwestern seas of Nansha Islands and the mouth of Beibu Bay

根据2012–2013年在南沙群岛西南部和北部湾口海域春秋两个航次的调查资料,分析了该海域鱼类种类组成、相对重要性指数和物种多样性等特征。结果表明,两个航次调查共鉴定鱼类504种,隶属于2纲31目129科294属;其中北部湾口海域出现鱼类301种,南沙群岛西南部海域出现鱼类357种。优势种数量较少,多以中小型鱼类为主,且季节间变化较大。春季多样性指数高于秋季,这主要是因为春季出现的大量鱼类为补充群体,而许多种类在秋季有向较深海区移动的趋势;南沙群岛西南部海域多样性指数高于北部湾口海域,这主要是由于南沙群岛西南部海域受水温和洋流的影响较大造成的。更替指数和迁移指数显示,秋季鱼类群落结构稳定性要低于春季,而且两个季节的鱼类群落结构都偏离平衡状态,主要是由鱼类的洄游和不同适温性鱼类的迁入迁出造成的。综合来看,南沙群岛西南部海域鱼类物种多样性和群落结构稳定性均高于北部湾口海域,在努力控制资源可捕量范围的同时,可合理开发南海中南部海域的渔业资源。

Based on fixed-point survey data in southwestem seas of Nansha Islands and the mouth of Beibu Bay in the spring and autumn of 2012 and 2013, we calculated the composition offish species, index of rela- tive importance （1R/） of each species, Margalef richness index （D）, Shannon-Wiener diversity index （H3, Pielou evenness index （J＇）, replacement index and migration index of the fish community. Results showed that a total of 504 species were identified involving 2 classes, 31 orders, 129 families, and 294 genera in the surveyed areas. There were 301 fish species in the mouth of Beibu Bay and 357 species in southwestern seas of Nansha Islands. The number of dominant species in autumn was higher than that in spring, and the number in the southwestern seas of Nansha Islands （SS） was higher than that of the mouth of Beibu Bay （SN）, with an obvious seasonal fluctuation. All diversity indexes during the spring survey were higher than those of the autumn survey because of recruitment in spring and the movement of fish species to the deep sea in autumn. However, all diversity indexes of SS were higher than that of SN due to the larger effects of sea temperature and currents in the southwestern seas of Nansha Islands. Results of the replacement index and migration in- dex showed that the fish community structure in autumn was less stable than that in spring and the commu- nity structure in the both seasons deviated from equilibrium because of fish migration and immigration and emigration of fishes with different thermophily. The integrated results showed that the species diversity and stability of fish community structure of SS were greater than those of SN. The fishery allowable catch should be controlled in a reasonable range and the fishery resources of the central and southern South China Sea should be exploited reasonably under the national supported policies. The stability of fisheries in the South China Sea is based on the high species diversity, therefore, it is also important to protect the diversity of species.