Tolerance and Avoidance Behavior towards Gas Supersaturation in Rock Carp Procypris rabaudi with a History of Previous Exposure

Abstract

Total dissolved gas (TDG) supersaturation on the upper Yangtze River basin is becoming increasingly serious because of the intense construction of high dams, posing a threat to resident fish. The tolerance and behavior characteristics of Rock Carp Procypris rabaudi preexposed to TDG‐supersaturated water were evaluated by placing juveniles (weight 6.4 ± 1.67 g, fork length 7.2 ± 0.7 cm; mean ± SD) in 35‐cm‐deep tanks at 130% supersaturation for 2.33 h as preexposure. Surviving fish were allowed 5 d of recovery in saturated‐equilibrium (100% TDG) water and then examined in an acute lethality experiment at TDG supersaturation values of 120, 125, 130, 135, 140, and 145%. The resulting median lethal times were 10.4, 4.6, 3.2, 2.1, 1.4, and 1.4 h, respectively. The preexposed fish showed a poorer tolerance to TDG‐supersaturated water than did a control group that were not preexposed for TDG above 120% supersaturation (P < 0.05 in cases where there was a significant difference between individual groups). Experiments on horizontal behavior and vertical behavior used the same preexposure routine, followed by 5 d of recovery in saturated‐equilibrium water. For all behavior experiments, both the preexposed and control groups showed significant avoidance responses to TDG‐supersaturated water; however, there were no significant differences between the preexposed and control groups.

Swimming Performance of Rock Carp Procypris rabaudi and Prenant's Schizothoracin Schizothorax prenanti Acclimated to Total Dissolved Gas Supersaturated Water

“…Our results showed that most of the Rock Carp and Prenant's Schizothoracin recovered within 2 d in the saturated-equilibrium water, which is consistent with the results of Dawley and Ebel (1975) and Wang et al (2015b). Wang et al (2015b) placed Rock Carp into 35-cm-deep tanks at 130% supersaturation for 2.33 h and then held them in saturated-equilibrium (100% TDG) water for 5 d. Their results indicated that these fish had a poorer tolerance to TDG-supersaturated water than did the control fish, although their horizontal and vertical behaviors were not significantly different. Our experiment showed that the swimming speed of Prenant's Schizothoracin after 2 d of recovery was significantly lower than that of the control fish, whereas that of the Rock Carp under the same treatment reached baseline levels.…”

“…Gas bubbles were visible on the fins of the two species in this study, and these fish also suffered mortality within 4 h of TDG supersaturation (15.6% for the Rock Carp and 5.0% for the Prenant's Schizothoracin). The results indicated that Prenant's Schizothoracin was more tolerant of TDG-supersaturated water than were Rock Carp during the 4-h exposure treatment, which was consistent with the results of previous studies (Wang et al 2015a(Wang et al , 2015b.…”

“…The supersaturation level was between 129% and 131% TDG, which is representative of conditions downstream from the dams on the upper Yangtze River basin (Li et al 2009;Qu et al 2011). The TDG-supersaturated water was generated using a pump and a compressor (Wang et al 2015a(Wang et al , 2015b, and the dissolved gas levels were monitored by a TDG measuring instrument (Tracker; Point Four Systems, Inc., Apopka, Florida) at the surface of the water tank.…”

“…During the flood season, water is allowed to spill over dams through discharge structures, and air is trapped in the plunge pools downstream of the dams, thus leading to increased total dissolved gases (TDGs) in the downstream river (Hibbs and Gulliver 1997;Qu et al 2011). Supersaturation with TBG can affect fish and other aquatic resources downstream of dams, and a high level of TDG supersaturation can easily cause gas bubble disease (GBD) and mortality in fish (Weitkamp and Katz 1980;Weitkamp 2008;Chen et al 2012;Wang et al 2015aWang et al , 2015b. A serious supersaturation problem existed in the Columbia River basin (USA), and GBD in fish resulting from TDG supersaturation has long been a cause of concern (Ebel 1969;Meekin 1971;McGrath et al 2006;Arntzen et al 2008;Geist et al 2013).…”

“…To study the effect of TDG supersaturation on the swimming performance of fish living in the upper Yangtze River, we selected Rock Carp and Prenant's Schizothoracin as our experimental species and then assessed the U crit and U burst values of fish exposed to TDG-supersaturated water. On the basis of previous studies, we proposed two hypotheses: (1) TDG exposure (129-131%) for a short time (2-4 h) would result in lower swimming speeds and even mortality (Wang et al 2015a(Wang et al , 2015b, and (2) swimming speeds would return to normal levels after sufficient recovery time (2 d; Schiewe 1974; Dawley and Ebel 1975;Wang et al 2015b). The results of this study can be used to inform the operation of hydropower stations and contribute fundamental data for establishing water-related environmental standards in China.…”