Hatching rate of Chinese sucker ( Myxocyprinus asiaticus Bleeker) eggs exposed to total dissolved gas (TDG) supersaturation and the tolerance of juveniles to the interaction of TDG supersaturation and suspended sediment

Abstract

Flood discharge containing excessive suspended sediments (SS) can result in total dissolved gas (TDG) supersaturation downstream of dams. It has been confirmed that high TDG levels and excessive SS cause serious threats to fish survival. To explore the effects of TDG supersaturation on the hatchability of Chinese sucker (Myxocyprinus asiaticus Bleeker) eggs, eggs were exposed to 100%, 125%, 130% and 135% TDG supersaturated water. The results showed that the hatching rates were 78.25%, 75.35%, 71.30% and 67.50% at the 100%, 125%, 130% and 135% TDG respectively. The hatching rate decreased with increasing TDG levels. Furthermore, acute lethality experiments were carried out to investigate the interaction of TDG supersaturation and SS on Chinese sucker. Half-year-old juveniles were exposed to TDG supersaturated water with SS concentrations of 0, 200, 600 and 1,000 mg/L, and the TDG levels were 125%, 130%, 135% and 140% respectively. The fish exhibited abnormal behaviours and signs of gas bubble disease. Mortality increased with increasing TDG levels and SS concentrations. The Chinese suckers only survived for 2.5 hr at 140% TDG and 1,000 mg/L SS. Moreover, an increase in SS in TDG supersaturated water could cause a decrease in the median lethal time (LT 50 ). When the TDG level reached 140%, the LT 50 declines significantly at 600 and 1,000 mg/L SS. The interaction of TDG supersaturation and SS was significant at LT 50 (F = 22.81, df = 9, p < 0.001). The results indicate that the combined effect of TDG and SS could be great on Chinese sucker. K E Y W O R D SChinese sucker (Myxocyprinus asiaticus Bleeker), hatching rate, median lethal time (LT 50 ), suspended sediment, Total dissolved gas supersaturation

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

“…Previous studies have demonstrated that GBD symptoms are often found in fish exposed to TDG-supersaturated water [28][29][30][31]. Some typical GBD symptoms were described, such as excessive bubbles on the fins, exophthalmia, haemorrhages and swelling of the swimming bladder [6,22,32,33]. In this study, juvenile grass carp subjected to TDG-supersaturated water exhibited caudal fin bleeding, dorsal fin bubbles, loss of scales and abdominal swelling.…”

“…Ji et al [42] reported that Prenant's schizothoracin had higher mortality at high TDG levels (130% and 135%) than at low TDG levels (110% and 115%). Some researchers found that the tolerance of Chinese sucker decreased with increasing TDG levels [22,43]. In this study, the LT 50 values of large and small juvenile grass carp at the 130% TDG level (36.55 and 88.13 h, respectively) were much higher than those at the 140% TDG level (6.37 and 35.88 h, respectively) ( Table 1).…”

“…The experimental system for generating TDG-supersaturated water was described by Li et al [22]. The system consisted of water flumes, water tanks, a water pump, a pressure vessel and an air compressor.…”

Effect of Total Dissolved Gas Supersaturation on the Survival of Bighead Carp (Hypophthalmichthys Nobilis)

“…In China, previous studies have shown that different benthic endemic species in the Yangtze River have diverse tolerance to TDG. According to Li et al, (2019), the LT 50 (50% survival probability) values of the Chinese sucker were 6.1, 4.5 and 3.1 h at 130, 135, and 140% TDG, respectively. In addition, Wang et al, (2015) [39] indicated that Prenant's schizothoracin in TDG supersaturated water at levels of 130, 135, and 140% possessed LT 50 values of 8.7, 8.0 and 4.6 h, respectively.…”

“…TDG supersaturated water was generated by a system that is described in detail by Li et al, (2019) [27]. In the system, a compressor produced compressed air, which was injected into an autoclave in addition to the water from the water flume to create high TDG supersaturated water.…”