Impacts of turbidity on the behaviour, thermal- and hypoxia tolerance of the Endangered Lake Chubsucker across lab and field contexts

Increased aquatic turbidity often co-occurs with other environmental stressors, such as warming waters and low oxygen (hypoxia), which may impact the behaviour and physiology of aquatic organisms. Using three experiments, we examined whether chronic turbidity exposure affects the standard metabolic rate, hypoxia tolerance, and growth of the Endangered Lake Chubsucker (<i>Erimyzon sucetta</i>) and whether acute exposure to turbidity impacts the behaviour and thermal tolerance of this species. Our results suggest that chronic exposure to turbidity decreases growth and decreases critical oxygen tension (Pcrit) in Lake Chubsucker relative to the chronic exposure to clear water. Across turbidity treatments, the mean Pcrit and oxygen level at loss of equilibrium were 26.3% air saturation and 4.7% air saturation respectively. When Lake Chubsucker were acutely exposed to medium turbidity, they exhibited fewer calm behaviours compared to when fish were exposed to the control or low turbidity. However, turbidity exposure did not impact thermal tolerance in both the lab and field experiments. As this is the first study to house and test environmental tolerances of Lake Chubsucker in Canada, our research provides unique insights into this Endangered species that may inform conservation efforts.