ASFB 2018 The effects of hypoxia on Australian freshwater fish species (#15)
Persistent hypoxic conditions in aquatic systems are becoming more frequent worldwide, causing large-scale mortalities to aquatic fauna. Studies investigating hypoxia tolerance of fish are limited and tend to be focused on marine species and short-term exposure. There has been minimal effort to understand the implications of long-term exposure on fish and their ability to acclimate. Three native Australian freshwater fish species were exposed to normoxic and hypoxic conditions at different temperatures for between 7 days and 10 months, before being placed in individual respirometry chambers to measure a range of physiological responses including metabolic rate, hypoxia tolerance and acclimation ability. Hypoxia tolerance varied among species, but long-term exposure improved tolerance to hypoxia. While prior exposure to hypoxia may allow fish to cope with hypoxic conditions better in the long-term, acclimation time was inversely related to tolerance, suggesting that resistance to hypoxia might decrease as a function of exposure time. Our study fills a much-needed gap in understanding how freshwater species acclimate to hypoxia; in particular how exposure to prolonged periods of hypoxia and elevated temperatures affect organisms physiologically.
