The practice and effectiveness of ecological operation experiment on spawning of the four major Chinese carps by Three Gorges Reservoir

Wei Xu,Jiangping Tao,Xiaojuan Chen,Cao Jun,X Lei,S Cai,Y Yu,H Li

doi:10.1051/matecconf/201824601084

Abstract

Eco-operation experiment by the Three Gorges Reservoir was carried out ten times to facilitate spawning of the four major Chinese carps in the lower reaches of Yangtze River, from 2011 to 2017. To get knowledge of fish spawning response to man-made flood process, and also assessing the positive effect of eco-operation on fish spawning, fish eggs were monitored daily by drift-net method, in a fixed profile in Shashi reach between mid-May to mid-July each year. Basing on the consecutive data and research for seven years, the practice and effectiveness of TGR eco-operation experiment on fish spawning were summarized and prospected. The main findings were as follows: eco-operation experiment usually operated in a suitable condition from late May to the end of June. Based on the hydrological monitoring data in Yichang station, the continuous days of rising limb varied from 3 days to 9 days, the mean diurnal increment of water level varied from 0.43 m to 1.30 m, and the water temperature varied from 20℃ to 24℃, except in 2013 that only below 18℃, during eco-operation period within seven years. According to the fish eggs monitoring data in Shashi reach, annual egg abundance of the four major Chinese carps ranged from 116 to 610 million, grass carps and silver carps were two dominant species with proportion of more than 80%. Egg abundance of the four carps produced in eco-operation period accounted for about 38% averagely of total amount in the whole monitoring period, with nine floods in total of thirty-three floods. Four indicators representing fish spawning performance, the time interval from water rising to spawn happening, duration time of spawning, extent of spawning grounds, and spawning scale, were calculated in each spawning event corresponding to each flood process. All indicators gave evidence that spawning performance of the four carps were better in eco-operation period, compared with other routine operation period. It was concluded the Three Gorges Reservoir eco-operation had done its work on boosting spawning of the four major Chinese carps, but further and foremost research should be developed on the following aspects, quantifying the eco-operation effect, optimizing the eco-operation index, and extending the eco-operation target to other important life history stage of fishes.

Highlights

The four major Chinese carps were common name of four endemic fishes consist of grass carp, silver carp, bighead carp and black carp, as they played very important role in both cultivation and capture freshwater fishery in China [1, 2]
Yangtze River was a natural origin of the four carps, and their major habitats largely located in the middle reach, with spawning scale from Yichang to Chenglingji reach contributed to 42.7% of Yangtze mainstream historically [3, 4]
The requirements of FMCC spawning were specific and rigorous, such as typically spawned in large and turbid rivers; the lowest water temperature for spawning was 18°C, spawning peak occurred at 21 to 24°C, increase of river flow was the key triggering factors, eggs and larvae must drift in the current until they matured enough to migrate into

Summary

Introduction

The four major Chinese carps were common name of four endemic fishes consist of grass carp, silver carp, bighead carp and black carp, as they played very important role in both cultivation and capture freshwater fishery in China [1, 2]. According to TGP operation rules, The Three Gorges Reservoir (TGR) would balance water discharge both in May and June, which caused flood process in downstream more smoothly and discharged water temperature lower than the natural condition. Basing on the monitoring data in Shashi section from 2011 to 2017, this paper focused on three aspects, the implementation of TGR eco-operation, the spawning trait of the four major Chinese carps, and the effect of TGR eco-operation on fish spawning. Table. statistics of eco-operation implementation from 2011 to 2017 year the date during period of TGR eco-operation the starting discharge flow of TGR mean diurnal increment of discharge flow continuous days of flow increase mean diurnal increment of water level in Yichang mean water temperature in Yidu section

Spawning time and frequency

Spawning location and scale

Findings

Spawning response to hydrograph