A Laboratory Study Comparing the Effects of Acute Oxygen Depletion on Different Populations of Embryonic Salmon

The eggs of salmon are exposed to a range of environmental stressors in their natural hyporheic environment. One of the most frequently observed of these stressors is oxygen depletion. Sedimentation has long been associated with reduced oxygen supply to incubating embryos. More recently, however, studies have found that the hyporheic zone can experience hypoxia and anoxia due to the influence of deoxygenated groundwater. The relative influence of groundwater on the hyporheic zone varies between rivers, stretches of rivers and redds within the same stretch.

The results presented here are from a study that aimed to determine the potential effects of oxygen sags such as those known to characterise upwelling groundwater, on the incubation success of Atlantic salmon. A unique egg incubation facility at the University of Southampton was used to replicate oxygen sags found in the wild. Three oxygen sag treatments, along with one control and a chronic oxygen depletion treatment, were compared for their effect on incubation success (survival and sublethal effects).

In addition, four different UK Atlantic salmon populations were exposed to these treatments and their relative responses were compared. This provided important information about the potential adaptation of different salmon populations to oxygen stress.