Lethal Effect of Total Dissolved Gas-Supersaturated Water with Suspended Sediment on River Sturgeon (Acipenser dabryanus)

Abstract

High total dissolved gas (TDG) levels and excessive suspended sediment (SS) concentrations pose serious threats to fish survival during flood season. However, little information is available on the effects of TDG supersaturation with varying SS concentrations on fish. In this study, laboratory experiments were performed to investigate the effects of TDG supersaturation with varying SS concentrations on five-month-old river sturgeons (Acipenser dabryanus). The test fish were exposed to combinations of SS concentrations (0, 200, 600 and 1,000 mg/L) and TDG levels (125, 130, 135 and 140%), and their mortality and median lethal time (LT50) were quantified. The fish showed abnormal behaviors (e.g., quick breathing, fast swimming and an agitated escape response) and symptoms of gas bubble disease (GBD). SS increased the mortality of river sturgeon exposed to TDG supersaturation. Furthermore, the LT50 values at 125% TDG were 4.47, 3.11, 3.07 and 2.68 h for the different SS concentrations (0, 200, 600 and 1,000 mg/L, respectively), representing a significant decrease in LT50 with increasing SS. However, at higher TDG levels (130–140%), there was no significant increase in LT50 with increasing SS. Therefore, river sturgeon showed weak tolerance of TDG-supersaturated water with SS.

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

“…Previous laboratory studies also showed that juvenile Leptobotia elongata had a better tolerance than juvenile Schizothoracin prenanti (Wang et al, 2015; Yuan et al, 2017). Of the endemic species in China, juvenile Leptobotia elongata and Schizothoracin prenanti have a longer semi‐lethal time than other species when exposed to TDGS (Cao et al, 2016; Feng et al, 2019; Liu et al, 2019). The results of this study suggest that more deaths may occur for other endemic Chinese fish during flood discharge.…”

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

“…Subsequently, the effect of gas supersaturated water on Oncorhynchus tshawytscha, Oncorhynchus and Salmo gairdneri were investigated in the Nechako River and the Columbia River [ 2 , 11 ]. In China, some studies have been carried to estimate the effect of TDG on endemic species of Yangtze River (e.g., Acipenser dabryanus, Schizothorax prenanti and Procypris rabaudi ) in the laboratory [ 17 , 18 , 19 ]. However, relatively few studies have investigated the effect of TDG supersaturation on fish in natural rivers.…”

“…The possible explanation for this finding is that the compensation depth of water decreased the development of GBD [ 34 ]. Previous research demonstrated that higher TDG level (>125%) led to high mortality (nearly 100%) in fish after 96 h of exposure [ 13 , 19 , 22 , 31 ]. Relatively high survival probabilities for juvenile Procypris rabaudi and juvenile Myxocyprinus asiaticus were observed in the study.…”

“…This may be related to the peak TDG levels that occurred during the test ( Figure 2 ). In addition, existing results showed that suspended sediment might accelerate fish death in TDG-supersaturated water [ 19 , 21 , 22 ]. For example, Li et al [ 22 ] found that an increase in suspended sediment concentration (from 200 to 1000 mg L −1 ) increased mortality (from 10 to 70%) of juvenile Myxocyprinus asiaticus exposed to 125% TDG for 4 h, while increasing suspended sediment concentration (from 200 to 1000 mg L −1 ) caused 20 to 81% mortality in juvenile Procypris rabaudi exposed to 125% TDG for 10 h [ 21 ].…”

“…In 2014, the flood discharge at Xiluodu Hydropower Station caused the death of 40 tons of fish. Recently, many studies have been performed on the impact of TDG levels on the supersaturation tolerance of fish in the Yangtze River, for example, Acipenser dabryanus, Procypris rabaudi , Hypophthalmichthys nobilis, Myxocyprinus asiaticus and Schizothorax prenanti [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. However, most of these studies have been executed in the laboratory.…”