From email from Reclamation (Erik Knight):
Currently flows in the Gunnison River through the canyon are about 950 cfs. We expect no changes to this flow rate until mid-October when flows will be reduced to accommodate the brown trout spawn. River flows should be around 600 cfs during the time of the spawn. This will continue until the conclusion of the spawn in mid-November at which point flows in the river will increase to around 1000 cfs. Flows through the Black Canyon may increase again in December as releases from the Aspinall Unit will most likely need to be higher than 1000 cfs to lower Blue Mesa Reservoir to the Dec 31st winter target elevation.
More Aspinall Unit coverage here.