南海西北部陆架区鱼类的种类组成与群落格局

Fish species composition and community pattern in the continental shelf of northwestern South China Sea

根据2006—2007年在南海西北部陆架区海域进行的4航次底拖网调查数据,对该海域鱼类的种类组成和群落格局进行分析。调查共采获鱼类262种,隶属于20目102科。以冬季出现种类数最多,为166种;夏季和秋季次之,分别为161种和155种;春季最少,为135种。运用聚类分析和非度量多维标度(NMDS)方法分析了南海西北部陆架区鱼类群落结构的空间分布。研究表明,该海域鱼类可划分为5个群落,分别为粤西沿岸群落(群落Ⅰ)、海南岛东南沿岸群落(群落Ⅱ)、海南岛东部深海群落(群落Ⅲ)、过渡群落(群落Ⅳ)和混合群落(群落Ⅴ)。ANOSIM检验表明,各群落间鱼类组成的差异极为显著(R=0.847-0.939,P<0.001)。鱼类群落格局的变化与海流和水深关系密切,有较明显的沿水深梯度分布的规律。咸淡水鱼类在雷州半岛东部的冷涡区域,形成群落Ⅰ;南海暖流控制区域内的深海鱼类,形成群落Ⅲ;在南海暖流最为强劲的冬季,研究区域内大部分鱼类集结为混合性群落Ⅴ;琼东南沿岸的上升流区内形成群落Ⅱ;沿岸流强劲的夏、秋季,在沿岸流和上升流交汇处,形成过渡性群落Ⅳ。

To understand fish species composition, community pattern, dominant species and seasonal variation in the continental shelf of northwestern South China Sea, four otter trawl surveys were conducted in January and August 2006, and April and November 2007, representing winter, summer, spring and autumn, respectively. Sixteen stations were assigned in each otter trawl survey along the coastlines from eastern Leizhou Peninsula to southeastern Hainan Island. Fish collection and data analysis followed the National Marine Survey Standards （ GB/T12763.6--2007 ）. Totally 262 fish species, from102 families and 20 orders, were collected in the four seasonal surveys. The results revealed that the highest species diversity was in winter with 166 species recorded and the lowest was in spring with 135 species recorded; 161 and 155 species were recorded in summer and autumn, respectively. The Order Perciformes was the most important fish group in the continental shelf of northwestern South China Sea; the highest species diversity recorded was the Perciformes in all four seasons, and g0 out of 72 species recorded year-round belonged to the Perciformes. Species found in all four seasons contributed to 80.34% of total fish biomass. Ninety-one species found only in a single season contributed to 1.62% of total fish biomass. The spatial pattern of fish communities was analyzed using the hierarchical clustering and non-metric multi- dimensional scaling （NMDS） , five fish groups were indentified. The Group I , recorded in all four seasons, was located in the coastal waters of western Guangdong Province and consisted of 3 or 4 stations. The scale and the distribution area of the Group I were stable among seasons. The Group I1 , recorded in spring, summer and autumn, was located in the coastal waters of southeastern Hainan Island and consisted of 6--9 stations. The scale and the distribution area of the Group 1I had seasonal variation. The Group Ⅲ, recorded in spring, summer and autumn, was located in the deep waters of eastern Hainan Island and consisted of 4 stations. The scale and the distribution area of the Group Ⅲ were stable. The Group IV as a transitional community, recorded in summer and autumn only, was located in the deep waters of eastern Hainan Island and consisted of 1--3 stations. The scale and the distribution area of the Group IV were small and changed largely with season. The Group V as a mixed community, recorded in winter only, was also located in the deep waters of eastern Hainan Island and consisted of 13 stations. The scale and the distribution area of the Group V were the largest among the 5 groups. Based on the analysis of similarities （ ANOSIM）, the results showed the significant differences （ R = 0. 847-0. 939, P 〈0. 001 ） in fish community pattern for all four seasons. Although the station combinations in each fish community had seasonal variation, the correlation coefficients on the community similarities between spring and summer, between summer and autumn and between autumn and winter were 0. 780, 0. 630 and 0. 777, respectively. The variations of fish community pattern are closely related to ocean currents and depth. The brackish fishes distributed in the cold eddy area of eastern Leizhou Peninsula and contributed to the Group I ~ The deep sea fishes along the South China Sea Warm Current in eastern Hainan Island contributed to the Group Ⅲ. In winter wih the strongest South China Sea Warm Current recorded in the deep waters of eastern Hainan Island, the area was dominated by fishes from the mixed Group V. Because of the upwelling in the coastal waters of southeastern Hainan Island the area was dominated by fishes from the Group Ⅱ. In summer and autumn, the coastal current was strong and mixed with the upwelling in the deep waters of eastern Hainan Island ; therefore, the area was dominated by fishes from the transitional Group 1V. This study provides scientific evidences for further sustainable fisheries development and conservation in the continental shelf of northwestern South China Sea.