Salinity Tolerance of the Endangered Atlantic Whitefish (Coregonus huntsmani): Unravelling the Conservation Physiology of an Enigmatic Fish

Abstract

Amidst the ongoing global decline in biodiversity, the preservation of at risk, endemic species is increasingly important. The Atlantic Whitefish (Coregonus huntsmani) is an endangered, anadromous fish endemic to Nova Scotia, Canada. The only remaining population, located in the Petite Rivière watershed, has been effectively isolated in three lakes by dams since at least 1901; these dams are thought to have prevented anadromous migrations. Restoring anadromy is an important part of the recovery strategy for Atlantic Whitefish. However, the effects of salt water on the physiology and performance of the Petite Rivière population following a century without anadromy are not fully understood. I investigated the effect of salinity (0, 15, 30 ppt) at two different temperatures (~12 – 17oC) on the growth, condition, baseline stress level (blood lactate and glucose, plasma cortisol) and osmoregulatory capacity (plasma ion content and osmolarity) of lab-bred, F1 juvenile Atlantic Whitefish. I also conducted preliminary experiments of swimming performance and oxygen uptake during exercise but the sensitivity of Atlantic Whitefish to tail damage acquired in the respirometer, forced discontinuation of swim trials. I found that treatment salinity did not significantly affect growth, condition factor, or indicators of stress. There was a slight increase in total plasma osmolarity in response to full-strength seawater (30 ppt), but no significant differences among salinities in plasma Na+ or Cl concentrations. Fish sampled following an increase in ambient temperature from approximately 11.66°C to 16.55°C did exhibit significantly lower relative condition and higher blood lactate concentrations. Together, these results indicate that the Atlantic Whitefish in the Petite Rivière population grow and generally perform well in brackish (15 ppt) and full strength seawater (30 ppt). Therefore, they are capable of tolerating the salinity changes associated with an anadromous migration, but may be sensitive to temperature increases in their natural environment.