Minnows -- When do they become active after winter?

A couple of questions regarding minnows:

1) What happens to minnows (creek chubs/dace/shiners/etc.) during the
winter? Creeks that are abundant during the summer seem barren during
the cold months of the year. Can they be harvested in the winter, or
must I continue shelling out 12/$5 to a bait shop?

2) At what time of year can I expect them to return?

I am (growing impatient g) in the Eastern Ontario/Western Quebec area.

Thanks!

--
DC

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