长江口口门区潮下带水域鱼类群落组成的季节变化

根据2006～2007年对长江口口门区潮下带鱼类的监测数据，分析了该水域鱼类群落组成的季节变化特征。结果表明：本次调查采获鱼类42种，隶属21科。生态类群以海洋鱼类种类最多（27种），其次为河口定居种（10种），而淡水鱼类、溯河产卵洄游鱼类和降海产卵洄游鱼类种类数很低。S1站点和S2站点类似，均以棘头梅童鱼（Collichthys lucidus）、刀鲚（Coilia ectenes）、龙头鱼（Harpodon nehereus）为优势种。两站点鱼类群落在空间上无显著差异，而时间上均有明显的季节变化，冬季和初春的样品聚为一组（Ⅰ组），夏、秋季的样品聚为一组（Ⅱ组）。通过SIMPER分析可知，两组间的平均相异性较高，达7303，共有17种鱼类对组间的贡献超过90%，如日本鳗鲡（Anguilla japonica）、棘头梅童鱼、矛尾虾虎鱼（Chaeturichthys stigmatias）、刀鲚、焦氏舌鳎（Cynoglossus joyneri）、龙头鱼等。

SEASONAL CHANGES OF FISH COMMUNITY COMPOSITION IN THE SUBTIDAL WATER IN THE MOUTH AREA OF YANGTZE ESTUARY

Based on the surveys of fishes in the subtidal water of the mouth area of Yangtze estuary between June November in 2006 and January March in 2007, we analyzed the seasonal changes of fish community composition in this area. A total of 42 fish species belonging to 21 families were collected. The lengths of all fish species were almost lower than 20cm, which meant the fish community composition mainly dominated by the young or small size fishes in the subtidal water areas. The guild of marine fishes (27 species) has the largest number of species, followed by estuarine resident fishes (10 species), while the other guilds of freshwater, anadromous and catadromous fishes had the lower number species. As for as the live layers of subtidal fishes, the most fish species was the demersal fishes (about 23 species), followed by the surface or pelagic fishes (14 species), lowest the lower level of fishes (only 5 species). The dominant species contributing above 15% of the total fish abundance were spinyhead croaker Collichthys lucidus, estuarine tapertail anchovy Coilia ectenes, leading fish Harpodon nehereus in station S1, which was similar with station S2. It found that there was higher similar in fish community composition between station S1 and S2, so it suggested that no obvious difference existed in the subtidal fish community in the mouth area of Yangtze estuary. However, we also found that there were obviously seasonal changes in fish abundance and species between these two sampling stations. Using the methods of group average cluster analysis and nMDS ordination, the subtidal fish community was classified into groupⅠ(samples collected from winter to early spring) and group Ⅱ (samples collected from summer to autumn). Through the SIMPER soft analysis on the fish community, we found the average similarity in group Ⅰ was 63% and accumulative contribution of 5 fish species was more than 90%, including Anguilla japonica, Collichthys lucidus, Coilia ectenes. In group Ⅱ, the average similarity was 442% and accumulative contribution of 7 fish species was more than 90%, such as Collichthys lucidus, Coilia ectenes, Harpodon nehereus, Trypauchen vagina, Odontamblyopus rubicundus, Stolephorus chinensis and Setipinna taty. Moreover, the average dissimilarity between the two groups reached 7303% and the accumulative contribution of 17 fish species was more than 90%, such as Japanese eel Anguilla japonica, spinyhead croaker Collichthys lucidus, spear tail goby Chaeturichthys stigmatias, estuarine tapertail anchovy Coilia ectenes, Joyners tonguesole Cynoglossus joyneri and leading fish Harpodon nehereus