Effect of total dissolved gas supersaturation on the tolerance of grass carp (Ctenopharyngodon idellus)

Abstract

Background: Total dissolved gas (TDG) caused by the rapid outflow of water from dams may threaten the survival of fish. However, few studies have assessed the impact of fish size on their tolerance to TDG supersaturation in the Yangtze River. To investigate the influences of fish size on the TDG supersaturation tolerance of fish, juvenile grass carp (Ctenopharyngodon idellus) of two sizes were subjected to TDG-supersaturated water at high levels (125%, 130%, 135% and 140%). Furthermore, varying flood flows may cause different TDG levels during the flood season. Fish may be subjected to low, chronic exposure to TDG before peak flooding occurs. However, TDG tolerance in fish subjected to high levels of TDG-supersaturated water after chronic exposure is rare. To further investigate the tolerance of juvenile grass carp subjected to acute exposure after chronic TDG exposure, juvenile grass carp were exposed to high levels of TDG-supersaturated water (125-140%) after receiving 96 h of chronic exposure (115% TDG). Results: In the single acute exposure and multiple exposures (acute exposure after chronic exposure), similar abnormal behaviours and symptoms of gas bubble disease (GBD) were observed in the juvenile grass carp subjected to the TDG-supersaturated water. No abnormal behaviour or mortality was observed in fish in the first chronic exposure of the multiple-exposure treatment. As the TDG level increased, the mortality of the large and small juvenile grass carp increased. The median lethal time (LT 50) for the large juvenile grass carp was 36.55, 21.75 and 6.37 h at 130%, 135% and 140% TDG levels, respectively, while the LT 50 value of the small juvenile grass carp was 88.13, 61.49 and 35.88 h at the same TDG levels, respectively. In addition, the LT 50 value of juvenile grass carp during acute TDG exposure after chronic exposure was 26.22, 7.54 and 5.34 h at 130%, 135% and 140% TDG levels, respectively. Conclusion: The tolerance of juvenile grass carp decreased with increasing TDG levels. The large juvenile grass carp had weaker tolerance to TDG-supersaturated water than the small juvenile grass carp. In addition, compared with juvenile grass carp subjected to single acute exposure, juvenile grass carp subjected to multiple exposures exhibited lower tolerance and were more vulnerable to the adverse effects of TDG.

Effects of continuous exposure to total dissolved gas supersaturation on swimming ability and recovery in grass carp (Ctenopharyngodon idella)

“…In the present study, grass carp exhibited high swimming speeds ( U crit : 4.13 BL/s; U burst : 9.03 BL/s) at 130% TDG. The present findings indicate that grass carp show stronger tolerance to TDG supersaturation than these other species (Prenant's schizothoracin, rock carp and Chinese sucker) (Fan et al, 2020; Huang et al, 2010; Li et al, 2019; Wang et al, 2015). Thus, we speculate that the grass carp has stronger swimming ability than these other three fish species.…”

“…Moreover, stress induced by TDG supersaturation may impair the ability of fish to pass through or over dams. In China, previous studies on the effects of TDG supersaturation on fish have been focused mainly on the tolerance, growth and avoidance behaviour of fish in the Yangtze River (Cao et al, 2015;Fan et al, 2020;Feng et al, 2019). Little research on the swimming speed of fish that experience intermittent exposure to TDG supersaturation has been reported (Wang et al, 2017(Wang et al, , 2018.…”

Behavioural response of brown trout (Salmo trutta) to total dissolved gas supersaturation in a regulated river

“…There may also be some evolutionary pressures on fish living in rivers such as Rysstad where total dissolved gas supersaturation has been present for several decades that selects for genes or phenotypes that are resilient to supersaturation; Gray et al (1982) suggested that higher supersaturation tolerance among Columbia River fish compared to controls from Italy might reflect a legacy of exposure in the Columbia. Cyprinids have better physiological tolerance to total dissolved gas supersaturation than salmonids (e.g., Fan et al, 2020; Wang et al, 2015), but what the mechanisms and whether they are heritable could be revealed in experiments and could include some experimental displacement field studies by transporting, tagging and observing behaviour and survival of fish from an affected and unaffected area. Matching our findings to observations of high mortality and symptoms of gas bubble disease of fish in the Otra River, however, are not in support of a hypothesis that this population is especially resilient to the trauma caused by total dissolved gas supersaturation.…”

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

“…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 ]. The water temperature and the size of the fish affect fish tolerance to TDG supersaturation [ 20 , 29 , 33 , 37 , 38 ]. The differences in TDG supersaturation tolerance between our results and the results of previous laboratory studies might be explained by the above factors.…”