Just one example, but I've encountered this many times over the past several years:
Two years ago on the Yough I crushed smalljaws one weekend when the water temp was 57-58 degrees. They were hitting everything I threw at them. The next weekend I fished all day long in the same locations. It had been freezing during the ensuing week and the water temp had fallen to about 49-50 degrees. I didn't get a single hit. I don't always check the water temp, but I noticed once it gets below 55 degrees it becomes much more difficult to find/catch smallmouth. A couple guys I know, who are much better fisherman than me, are able to locate them in the winter. But I think its pretty rare. As strange as it sounds, I've had more luck catching largemouths in cold water than smallmouths...
My understanding is that they winter in large groups in deep, slow water. They rarely eat. One time in the middle of winter I was walleye fishing in the Ohio River. I wasn't catching anything so I decided to put on a shiner and sink it on the bottom and just let it sit there. The baits sat there for a very long time and I caught two very large smallmouths. But I think it was pure luck.
"Part of being a Leftist is the smug conviction that you and people like you are smart, while everyone else is stupid and/or evil"
- T. Fleming