Heard that there are still new fish coming into the Oak, and the Finger Lakes tribs are still alive with fish.  Forsythia just bloomed here on Tuesday, that is usually the first couple of days of April.  You guys may still have more time left than you think, and you might hit early summer run fish toward the end of it.
 
As to the small fish in the tribs, when 2B and I first started going back in the early 80's, the oldtimers we met on the river all cried the blues about how the salmon and steel had ruined the fishing in the upper river.  The main river from Pineville up was a good brown trout fishery, and all the tribs had good brook trout populations.  Now you have to drive up above the reservoir to hit that, although if you get far enough upstream on the lower tribs, I am told there are still some brookies, but you have to sort through salmon and steel fingerlings to get at them.  The browns you are seeing might be remnants of those populations if they are resident.
 
L13