Field observations of the lethality characteristics of endangered and endemic fish under the stress of total dissolved gas supersaturation

Abstract

Total dissolved gas supersaturation (TDGS) caused by high dam discharge may threaten the survival of fish downstream. This study investigated the TDGS of Dadu River in the first 3 years (2016–2018) after the operation of Dagangshan hydropower station. The effect of TDGS on endemic fish was also evaluated for the first time in this study. Schizothoracin prenanti, Schizothorax davidi and Leptobotia elongata, which are endangered and endemic species in the Dadu River, were selected to evaluate the adverse effects of supersaturation on fish. We found that the supersaturation level varied from 115% to 127% in 2016, from 111% to 121% in 2017, and from 103% to 112% in 2018. The average water levels in these 3 years were 2.99, 2.34 and 1.14 m, respectively. The mortality of fish was positively correlated with TDGS and negatively correlated with water depth. The mortality of juvenile fish was highest in 2016, and increased TDGS had a greater contribution to fish mortality than the other factors. The highest mortality of adults occurred in 2017, and inadequate water depth was an important factor that caused fish mortality. The lowest mortality of both adults and juveniles occurred in 2018, and gas bubble disease in fish was almost never found. Even at shallow water depths, low TDGS (103%–112%) did not cause fish mortality.

Effects of Total Dissolved Gas Supersaturation on the Survival of Juvenile Procypris rabaudi and Juvenile Myxocyprinus asiaticus at Varying Water Depth in a Natural River

“…Compared with the surface water (0–0.3 m), deeper depths increased the survival of the test fish. This was consistent with the studies of Xue et al [ 27 ], Cao et al [ 28 ] and Yuan et al [ 30 ]. Furthermore, the water depth made a greater contribution to the survival of juvenile Procypris rabaudi than to the survival of juvenile Myxocyprinus asiaticus .…”

“…Furthermore, in the study of Yuan et al [ 30 ], 23% and 43% of adult Schizothorax prenanti survived at water depths of 0–1 m and 1–2 m in TDG-supersaturated water (average TDG: 117%), respectively. At the same water depths, adult Schizothorax davidi showed a higher survival rate (53%) after 6 d of exposure.…”

Advances in regulated river research in China

“…To address this problem, Wang et al (2021) compared five precipitation datasets, including three multiple interpolation datasets and two satellite remote sensing datasets, and evaluated their performances through a distributed hydrological model. Yuan et al (2021) coupled the MIKE SHE model with climate‐change scenarios from the Beijing Climate Center Climate System Model to predict runoff alterations under climate change conditions. These papers provide important reference points for improving the accuracy of precipitation models.…”

Tolerance and Growth of Adult Schizothorax prenanti Exposed and Re-Exposed to Supersaturated Gas Downstream of a Dam

“…The effects of TDG supersaturation are largely determined by both TDG level and water depth. For a given depth, the risk of mortality induced by TDG may be species-specific [7]. Knowledge of mortality rates and other effects of TDG on fish that are related to specific water depths allows us to predict the effects of dam spilling.…”