桂江鱼类物种组成及其群落时空变化格局的研究

为探究桂江鱼类群落结构现状，保护桂江鱼类物种多样性，于2015年1月（冬）、4月（春）、7月（夏）和10月（秋），对桂江平乐（S1）、昭平（S2）、五将（S3）、马江（S4）、木格（S5）、大郎（S6）、京南（S7）、倒水（S8）、梧州（S9）共计9个采样点，进行4次鱼类资源调查。分析了桂江鱼类物种组成、优势种和鱼类群落结构的时空变化；结果表明，本次调查共采集鱼类93种，隶属于6目、17科、 66属，其中以鲤形目为主（63种），占总种数的67.74%。鱼类相对多度（Relative density）显示，全年优势种为?（Hemiculter leucisculus），占总个体数的12.75%。不同季节的优势种有差异，冬季优势种为伍氏半?（Hemiculterella wui）、?和宽鳍鱲（Zacco platypus）；春季优势种不明显，个体数较多的有南方拟?（Pseudohemiculter dispar）和泥鳅（Misgurnus anguillicaudatus）；夏季优势种为?、大眼华鳊（Sinibrama macrops）和南方拟?；秋季优势种为?、莫桑比克罗非鱼（Tilapia mossambicus）和尼罗罗非鱼（T. niloticus）。无度量多维排序图（NMDS）和单因素相似性分析（ANOSIM）结果显示，除夏季与秋季之间外（P=0.178>0.05），其余季节之间鱼类群落结构存在显著性差异（P<0.05），这可能是珠江水系鱼类繁殖期（4-6月）及降水的季节性变化所致。采样点S1与S7、S8、S9，S6与S7、S8、S9，S2与S6、S9之间存在显著性差异。目前河流库区化、过度开采以及外来物种入侵是导致鱼类群落结构变化的主要原因。

Species Composition and Temporal-spatial Variation of the Fish Community in Guijiang River

Guijiang River is the primary tributary of Xijiang River, with a total length of 438 km and water area of 18,790 km2. In this study, we investigated the current status of fish resources in Xijiang River, focusing the field investigation on species composition, dominant species and spatio-temporal variations. The objectives were to provide scientific evidence for conserving biodiversity, sustainable development of fish resources and support the evaluation of river system health. In January, April, July and October of 2015, the investigation was conducted at nine sampling sites, representing different habitats; Pingle (S1), Zhaoping (S2), Wujang (S3), Majiang (S4), Muge (S5), Dalang (S6), Jingnan (S7), Daoshui (S8), Wuzhou (S9). Fish samples were collected using portable fishing equipment and nets, and all fish collected were identified by species. A total of 93 fish species were collected, falling into 166 genera, 7 families and 6 orders. Cypriniformes (63 species, 3 families) dominated the fish collected, accounting for 67.74% of the total species, followed by Perciformes (15 species, 8 families, 16.13%), Siluriformes (12 species, 3 families, 12.90%), Synbranchiformes (1species, 1 family, 1.07%), Anguilliformes (1 species, 1 family, 1.07%) and Cyprinodontiformes (1 species, 1 family, 1.07%). Hemiculter leucisculus was the most dominant species over the study period [relative density (RD) of 12.75%], but the dominant species varied with season; : Hemiculterella wui, Hemiculter leucisculus and Zacco platypus in winter; Hemiculter leucisculus, Sinibrama macrops and Pseudohemiculter dispar in summer; Hemiculter leucisculus, Tilapia mossambicus and Tilapia niloticus in autumn and no dominant species evident in spring. Non-metric multidimensional scaling (NMDS) ordination and one-way analysis of similarity (ANOSIM) showed that the fish community structure varied significantly with season (P<0.05), except for between summer (July) and autumn (October) (P=0.178>0.05). Structural differences were attributed to the effects of breeding season in the Pearl River (April-June) and seasonal variation in precipitation along the Guijiang River. Spatially, there were significant differences in the fish community between S1 and S7, S1 and S8, S1 and S9; S6 and S7, S6 and S8, S6 and S9; S2 and S6, S2 and S9. The static and deep water environment of reservoir after hydropower development, and alien species invasion were the primary factors leading to spatial changes in fish community structure.