1980—2007年大亚湾鱼类物种多样性、区系特征和数量变化

根据2004—2005年大亚湾海域底拖网鱼类调查数据，并结合1980—2007年的历史资料，分析了该海域鱼类的种类组成、区系特征、多样性、优势种和数量变化趋势.结果表明： 2004—2005年，大亚湾海域共记录鱼类107种，分属13目50科，以中下层鱼类的种类最多，为48种，其次是中上层和底层种类，分别为37种和21种.大亚湾鱼类区系具热带和亚热带特性，以暖水性种类占绝对优势，为97种，暖温性种类为10种.多样性指数以夏季最高（3.82），其次是冬季（3.37）和秋季（3.00），春季最低（2.40）.Pielou均匀度指数的季节变化情况与多样性指数相似.1980—2007年大亚湾海域鱼类群落特征发生了明显的变化：鱼类种类数减少，优势种更替明显.鱼类种类数由1980年的157种减少至1990年的110种，2004—2005年继续减少至107种；鱼类优势种由1980年以带鱼和银鲳等优质鱼为主，更替为以小型和低值的小沙丁鱼、小公鱼和二长棘鲷幼鱼为主.用包含年际变化趋势和季节性周期变化的回归模型模拟1980—2007大亚湾鱼类资源密度的变化，鱼类资源密度在1980—1999年和1990—2007年两个时期均呈下降趋势，但1990—2007年间下降幅度比1980—1999年间大；1980—1999年鱼类资源密度的季节波动幅度较平缓（振幅为0.099），而1990—2007年的季节波动较大（振幅为0.420），说明1990—2007年阶段大亚湾鱼类数量的季节变化更为显著.

Variations of fish species diversity,faunal assemblage,and abundances in Daya Bay in 1980-2007.

Based on the 2004-2005 otter trawl survey data and the 1980-2007 relevant historical records, this paper analyzed the variations of fish species composition, faunal assemblage, diversity indices, dominant species, and abundance in Daya Bay. In the 2004-2005 trawl survey, a total of 107 fish species were recorded, belonging to 50 families and 13 orders, among which, meso-demersal fish were predominant, with 48 species recorded, and followed by pelagic and demersal fishes, with 37 and 21 species, respectively. The fishes in the Bay belonged to tropical and subtropical fauna, with the dominance of warm water fishes (97 species) and warm temperate water fishes (10 species). The diversity index was the highest in summer (3.82), followed by in winter (3.37) and autumn (3.00), and the lowest in spring (2.40). The seasonal variation of Pielou evenness index mimickedthat of diversity index. In 1980-2007, the characteristics of fish community inthe Bay changed obviously. The species number reduced from 157 species in the 1980sto 110 species in the 1990s and to 107 species in 2004-2005, and the dominant species shifted from the high-value fishes such as hairtail and pomfret in the 1980s tolow-value fishes such as sardine fish, anchovy, and juvenile porgy. A non-linear regression model composed of inter-annual trend and seasonal cycle was usedto simulate the changes of fish stock density in 1980-1999 and 1990-2007, andthe results indicated that in the two periods, the fish stock density in the Bay all showed a decreasing trend, but the decrement was larger in 1990-2007 thanin 1980-1999. The seasonal variation of the stock density in 1980-1999 was relatively small, with an amplitude being 0.099, while that in 1990-2007 was relatively larger, with the amplitude being 0.420, illustrating that the fish abundance in the Bay had a larger seasonal fluctuation in 1990-2007.