The effect of total dissolved gas supersaturation on gas bubble trauma in juvenile rainbow trout (Oncorhynchus mykiss), juvenile kokanee (Oncorhynchus nerka), and two age classes of white sturgeon (Acipenser transmontanus)

Abstract

Hydroelectric dams are an important source of electricity globally, but they can also cause total dissolved gas (TDG) supersaturation in rivers. TDG supersaturation can harm fish through a condition called gas bubble trauma (GBT), which has been studied primarily in salmonids, such as rainbow trout and steelhead salmon (Oncorhynchus mykiss), but seldomly in non-salmonids like white sturgeon (Acipenser transmontanus). We assessed the vulnerability of juvenile rainbow trout (<1 year old), juvenile kokanee (Oncorhynchus nerka) (<1 year old), and two ages of white sturgeon (<1 year old and 3+ years old) to GBT. Bubble formation and the time to 50% loss of equilibrium (LOE) was quantified during exposure to nominal levels of 100%, 115%, 120%, and 130% TDG. We predicted that all three species would show similar times to 50% LOE at a given TDG level. However, time to LOE was longer, the proportion of fish with external symptoms of GBT was lower, and the proportion of fish with bubbles in the gills was higher or lower (dependant on age) in white sturgeon relative to rainbow trout and kokanee at a given TDG. The physiological basis for the difference is not known. However, it is important to consider species-specific differences in TDG sensitivity in the conservation of vulnerable species.