Lateral line pore diameters correlate with the development of gas bubble trauma signs in several Columbia River fishes

Growth rate, catalase and superoxide dismutase activities in rock carp (Procypris rabaudi Tchang) exposed to supersaturated total dissolved gas

Total dissolved gas supersaturation (TDGS) appears when the pressures of gases in a solution exceed the barometric pressures. TDGS is often caused by flood discharge at dams. It may lead to gas bubble disease (GBD) for fish and biochemical responses of selected fish and other aquatic organisms. The purpose of this study was to determine the impact of long-term TDGS levels on the growth and biochemical responses of rock carp (Procypris rabaudi Tchang) dwelling in the upper reaches of the Yangtze River. Three-year-old rock carp were exposed to TDGS levels at 100%, 104%, 108%, 112%, and 116% for 42 d. Samples were taken every 7 d after the start of the trial in order to determine catalase (CAT) and superoxide dismutase (SOD) activities in gill and muscle tissues. Samples were taken at Days 0 and 42 of exposure to determine growth rate. Little effect was found on growth rate in all treatment groups. SOD and CAT activities varied in different tissues, according to time of exposure and TDGS levels. The biochemical response of fish exposed to TDGS was more obvious in gill tissue than in muscle tissue. Surveys of SOD and CAT activities in different tissues offer important information about the effect of TDGS on the rare fish in the Yangtze River, and may help evaluate the risk to the aquatic eco-environment and aquatic ecosystem in the downstream of the Yangtze River.

Migration depths of adult steelhead Oncorhynchus mykiss in relation to dissolved gas supersaturation in a regulated river system

Adult steelhead Oncorhynchus mykiss tagged with archival transmitters primarily migrated through a large river corridor at depths >2 m interspersed with frequent but short (<5 min) periods closer to the surface. The recorded swimming depths and behaviours probably provided adequate hydrostatic compensation for the supersaturated dissolved gas conditions encountered and probably limited development of gas bubble disease (GBD). Results parallel those from a concurrent adult Chinook salmon Oncorhynchus tshawytscha study, except O. mykiss experienced greater seasonal variability and were more likely to have depth uncompensated supersaturation exposure in some dam tailraces, perhaps explaining the higher incidence of GBD in this species.