The Tolerance Characteristics of Resident Fish in the Upper Yangtze River under Varying Gas Supersaturation

Abstract

In circumstances where total dissolved gas (TDG) levels are variable, the peak TDG and duration are expected to be the dominant drivers of fish survival. Focusing on the peak TDG and duration in natural rivers, a laboratory experiment and field experiments in the upper Yangtze River were conducted with Prenant’s Schizothoracin (Schizothorax prenanti), a rare species inhabiting the upper Yangtze River, to examine the tolerance characteristics of fish under varying gas supersaturation levels. The results of the field experiments showed that TDG supersaturation in natural rivers changed greatly during the flood period due to reservoir regulation. The survival of fish was affected by TDG levels, water depth and TDG fluctuation range. A high TDG level, and shallow compensatory water depth caused fish mortality in the field experiment to be higher in September than in July. The results of the laboratory experiment showed that fish tolerance was lower under fluctuating TDG supersaturation than under constant TDG supersaturation. The tolerance of fish to TDG supersaturation varied depending on peak TDG and duration. Under the fluctuation range of 115–125%, fish survival in the 6 h–6 h cycle was significantly different from that in the 8 h–8 h cycle. The fluctuation cycle did not affect fish survival at the fluctuation range of 110–130%. Intermittent lower TDG supersaturation does not significantly increase the tolerance of fish. This study revealed the tolerance characteristics of resident fish in the upper Yangtze River to TDG supersaturation, which provides a reference to the ecological operation of reservoirs and may contribute to the protection of aquatic organisms.

Acute effects of gas supersaturation on Atlantic salmon smolt in two Norwegian rivers

“…Research on tolerances to TDG has so far focused on fish species from China and North America. Several field-and laboratory studies on the impact of and tolerance to TDG on endemic fish species have been conducted during the recent years in China (Wang et al, 2015;Cao et al, 2019;Ji et al, 2019;Xue et al, 2019;Deng et al, 2020). These studies were conducted due to sharp declines in several endemic fish populations after construction of hydropower constructions, and indicate that the tolerance to TDG vary among fish species.…”

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

“…Many studies have indicated that high levels of TDG supersaturation result in the increasing mortality of fish [40,41]. 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].…”

River Damming Impacts on Fish Habitat and Associated Conservation Measures

“…In natural rivers, TDG supersaturation is often caused by a change of water temperature (Bouck, 1984) and water falling (Rowland & Jensen, 1988). Dammed rivers can occur severe TDG supersaturation caused by flood discharge during flooding seasons (Figure 6a), resulting in serious impacts on fish downstream (Ji et al., 2019; Pulg et al., 2016). For instance, the Chief Joseph Dam released flow in excess of the 110% TDG compliance criterion (EPA, 1987) in the Columbia River, causing the downstream Wells Dam to be unable to comply with water quality criteria for 125 of 133 compliance‐mandated days in 2012 (Witt et al., 2017).…”