长江中游宜昌江段鱼类早期资源现状及水文影响条件

THE STATUS OF THE EARLY-STAGE FISH RESOURCES AND HYDROLOGIC INFLUENCING CONDITIONS IN THE YICHANG SECTION IN THE MIDDLE REACHES OF THE YANGTZE RIVER

为了解长江中游鱼类的早期资源现状, 2017年和2018年5—7月在长江干流宜都断面开展鱼类早期资源调查,采样网具包括弶网和圆锥网。调查期间共采集鱼卵21120粒和仔鱼2123尾。利用形态学和分子生物学等方法,鉴定鱼类5目9科37种。其中,鱼卵有29种,仔鱼有27种。2017年和2018年通过宜都断面的鱼卵径流量分别为124.45×10~8粒和101.07×10~8粒,优势种为四大家鱼和贝氏?(Hemiculter bleekeri);仔鱼径流量分别为16.43×10~8尾和8.29×10~8尾,优势种为贝氏?和寡鳞飘鱼(Pseudolanbuca engraulis)。根据发育期和流速分析,四大家鱼鱼卵来源于三峡大坝下游至宜都断面之间的产卵场,仔鱼来源于三峡大坝以上的产卵场。与2009—2010年相比, 2017—2018年通过宜都断面的鱼卵径流量增大了85.3%,尤其是四大家鱼的鱼卵径流量与2005—2012年相比增加了约13倍。冗余分析(Redundancy Analysis, RDA)结果显示,流量和流量日变化对产漂流性鱼卵密度有影响。研究结果表明, 2017—2018年仍有大量的鱼卵和仔鱼补充到长江中游江段。与历史数据相比,三峡大坝下游宜昌江段鱼类产卵规模有明显的增加,可能与长江中游四大家鱼亲鱼增殖放流和生态调度等保护措施的实施有关。为了更加有效地保护长江中游的鱼类资源,建议除了已经逐步实施的长江全面禁渔措施之外,还应恢复江湖连通,保护和修复长江中游河漫滩生境,继续开展重要经济鱼类亲本放流,以及开展生态调度。

In order to reveal the current status of the early-stage fish resources in the middle reaches of the Yangtze River,we conducted surveys in Yidu reach from May to July in 2017 and 2018.Sampling nets included a semi-conical net and a conical net.A total of 21120 eggs and 2123 larvae were collected.A total of 37 species in 9 families and 5 orders were identified using both morphological and molecular methods.Among which,29 and 27 species were identified in eggs and larvae,respectively.We estimated that 124.45×108 ind eggs and 16.43×108 ind larvae drifted through Yidu reach in 2017,while 101.07×108 ind eggs and 8.29×108 ind larvae drifted through Yidu reach in 2018.The four major Chinese carps and Hemiculter bleekeri were the dominant species in eggs while Hemiculter bleekeri and Pseudolanbuca engraulis were the dominant species in larvae.According to the analysis of development period and velocity,the eggs of the four major Chinese carps came from the spawning site in Yichang section between the lower reaches of the Three Gorges Dam and the Yidu section,and the larvae came from the spawning site above the Three Gorges Dam.Compared with data in 2009 and 2010,the runoff of fish eggs through Yidu section increased by 85.3%in 2017 and 2018,and the runoff of eggs of the four major Chinese carps increased by about 13 times compared with data from 2005 to 2012.Redundancy Analysis showed that flow charge and daily flow velocity were main environmental factors affecting reproductive activities of drifting eggs species.The results showed that after the impoundment of the Three Gorges Reservoir,a large number of fish eggs and larvae were replenished to the middle reaches of the Yangtze River.Compared with the data from 2005 to 2012,spawning size of pelagic eggs below the Gezhou Dam increased significantly which is related to the implementation of a series of protective measures,such as the breeding and releasing of the major four Chinese carps,the ecological regulation to promote the natural breeding of the major four Chinese carps and the management of banning fishing in the middle reaches of the Yangtze River in recent years.In addition to the gradual implementation in the Yangtze river’s comprehensive ban on fishing,we also suggest restoring the connectivity between rivers and lakes,protecting and restoring natural environment conditions of floodplains,releasing parental fish of economically important species,as well as carrying out ecological regulation,to effectively protect fish resources in the middle reaches of the Yangtze River.