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.
Highlights
Www.nature.com/scientificreports study was to investigate the effect of total dissolved gas (TDG) supersaturation with varying suspended sediment (SS) concentrations on river sturgeon from the upper Yangtze River
The above abnormal behaviors were found at other TDG levels (125, 130 and 135%)
Previous studies demonstrated that gas bubble disease (GBD) caused by TDG supersaturation resulted in the mortality of fish and threatened their survival downstream of dams during flood discharge[24,25,26]
Summary
Following acclimation and preparation of the experiment, 60 fish were moved into each experimental tank (length: 1 m; width: 0.6 m; water depth: 0.5 m). Mortality and median lethal time (LT50; the exposure time at which the mortality of fish reached 50% at a specific TDG level) were determined to investigate the effect of TDG-supersaturated water with SS on river sturgeon. The difference in LT50 among TDG levels was analyzed using one-way analysis of variance (ANOVA) followed by a least significant difference (LSD) test. A two-way ANOVA followed by a post hoc multiple comparison test (Tukey test) was executed in SPSS to determine the effect of TDG supersaturation with varying SS concentrations on river sturgeon. Data were expressed as the mean ± SD, and the significance level was set at P < 0.05
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