长江天鹅洲白鱀豚国家级自然保护区鱼类资源现状

Fish Resource Status in the White-Flag Dolphin National Nature Reserve of Tian-e-Zhou Oxbow,Yangtze River

了解湖北长江天鹅洲白鱀豚国家级保护区的鱼类资源现状,为豚类保护措施的制定提供参考,也为长江渔业资源的保护和管理提供依据。于2017-2019年在保护区水域进行了渔获物和渔业水声学调查。调查共采集到鱼类83种(亚种),结合历史资料,保护区共分布有鱼类154种(亚种),隶属于11目25科85属。历史资料中的71种在此次调查中未采集到,有7种为此次调查新增种类。长江干流和天鹅洲故道的优势种和鱼类密度均存在较大差别。在保护区长江干流江段,黄颡鱼(Tachysurus fulvidraco)和银鮈(Squalidus argentatus)为优势种,在天鹅洲故道,光泽黄颡鱼(Tachysurus nitidus)和贝氏歺又鱼(Hemiculter bleekeri)为优势种。长江干流和天鹅洲故道的鱼类资源平均密度分别为(0.40±0.38)和(0.94±0.81)尾/m^(3)。调查结果表明,保护区的鱼类资源仍处于衰退的进程中,需针对保护区不同水域采取不同的保护措施。

The White-Flag Dolphin National Nature Reserve of Tian-e-Zhou Oxbow is an important habitat of the Yangtze finless porpoise(Neophocaena asiaeorientalis).The reserve is located in the middle reach of Yangtze River and includes 89 km of the main stem in addition to the 21 km Tian-e-Zhou Oxbow.As the principal food of dolphins,fish resources play a key role in the ecosystem health of the reserve.In this study,we investigated the status of fish resources in the reserve using fish catch analysis and acoustic surveys focusing on species composition,distribution,density and structural characteristics of the fish community.The objectives were to provide a reference for dolphin protection as well as fishery resource conservation and management in the Yangtze River.Fish surveys were carried out at six sampling sites in the reserve during May of 2017,2018,2019 and October 2018.Each survey lasted 10 days and the acoustic survey was carried out only in May 2018.A total of 83 fish species(including subspecies)were collected during the investigation,and 7 species were recorded for the first time in the reserve.The field survey data,combined with historical data,indicate a total of 154 species and subspecies in the reserve,belonging to 11 orders,25 families and 85 genera.Thus,71 fish species recorded in the historical data were not observed in this survey.The dominant species and fish density in the Yangtze River main stem varied greatly from those in the Tian-e-Zhou Oxbow.Tachysurus fulvidraco and Squalidus argentatus dominated in the main stem,while Tachysurus nitidus and Hemiculter bleekeri dominated in the oxbow.The average fish densities were(0.40±0.38)ind/m^(3) in the main stem and(0.94±0.81)ind/m^(3) in the oxbow.Compared with historical data,protected species(such as Psephurus gladius)are rare,dominant species in the mainstream have changed markedly,and the trend toward miniaturization in the fish community is more obvious.Results indicate that fish resources are declining and countermeasures are necessary to conserve fish resources in the White-Flag Dolphin National Nature Reserve.