Darter "Hibernation"?

This last fall, I put @ 20-24 Rainbow Darters in my 150.
Over winter, I had the tank down to 45 degrees.
When I fed, the minnows & dace ate, and occasionally I'd see a big male darter or two, but that was it.
I didn't think any off the darters had died.
With spring moving in, the tank is now at 55 degrees and I lengthened the light cycle to reflect longer sunrise/sunset times.
When I fed this weekend, Blamo! All of a sudden every darter was out of the rocks!
Once again, there appears to be @20 + darters in the tank!
The males are very bright & most of the females appear gravid - awesome!

Question I have is; Will darters go dormant? I have easily 2-300# of rock in the tank which I think is where they were all hiding.
The bottom of the tank was a ghost-town over winter, and now it's very busy.

There's plenty of room to hide here-

Edited by creekcrawler, 13 April 2010 - 01:02 PM.

Dormant might be too strong a word, but darter metabolism would certainly slow down at 45 deg. F. I think extended exposure to water just above freezing would push them to something more like dormant. The coldest winter flowing water I've observed in north Alabama was 2 deg. C (~36 F) and the darters we seined definitely appeared less frisky than usual. If your fish are from Ohio, I'd guess that they probably did benefit some from a protracted period of fairly cold water.