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COSEWIC Assessment and Update Status Report on the Aurora Trout in Canada

General Biology

Reproductive Capability

Aurora Trout spawn in late October and early November when lake water temperatures are below 8°C. Sexual maturity is reached at age 2+ to 4+ years. The maximum known lifespan is 9 years. Spawning is thought to occur annually after sexual maturity is reached. The number of eggs produced by mature female Brook Trout is dependent on size. Ripe females in the native lakes ranged in size from 335 mm to 458 mm fork length. Brook Trout of that size typically produce 1000 (325 mm fork length) to 3000 (470 mm fork length) eggs (Vladykov 1956). 

Species Movement

It appears that the thermal requirements of Aurora Trout are similar to other Brook Trout (eg. Sale 1962). Brook Trout generally inhabit water temperatures below 20°C and when temperatures rise above that they seek cooler water by shifting their depth distribution or by inhabiting groundwater springs (Scott and Crossman 1973; Power 1980). At spawning time Aurora Trout will seek areas of groundwater upwelling on which to excavate redds.


A pH of at least 5.0 is required for successful reproduction and maintenance of self-sustaining populations (Beggs and Gunn 1986). Aurora Trout stocked into Whirligig Lake during the late 1980's when it was still quite acidic (pH 4.8) survived in small numbers, but they were physiologically stressed, could not reproduce and had shortened lifespans.

The spawning sites that have been identified to date are all on groundwater springs which is typical of Brook Trout on the Canadian Shield (Noakes and Curry 1995). We speculate that the failure of stocked Aurora Trout to reproduce in most non-native lakes is due to the unavailability of suitable groundwater sites for spawning in those lakes.