While fishing this weekend the water temp was 63 to 67 depending on the area of the lake. The weekend before that the water temp was in the 70's. Is this a shock to the fish and shad?

Close to the end of the day the shad were migrating to the back of the coves by large numbers (big schools. Do they stay there or do they move in and out with water temp?
Thanks for any ideas or help.....

"Shock" can be relative. Fish live there all the time and are acustomed to the temp fluctuations and barometric pressure changes. They just adapt and adjust. They move up and down the water column and back and forth into the coves or deep water for their preferred temp locations. I have seen shad "kills" in the winter time after a SEVERE change but it us usually not after just one cold front. When the lake get's to a point where there is a limited amount of locations that can adjust to their living parameters then some will die. Southern Lakes tend to not be as severe with the Winter conditions as with northern or Mid Central United States lakes. Some of our lakes never really get into a "Winter" Pattern like the northern ones. For example: Sam Rayburn will often times NOT go from a Fall Pattern (Back of cove shad pattern) to a true winter pattern (deep water suspended fish). It will go straight from a Fall Pattern to a Pre-Spawn (or Pre-Pre Spawn) pattern. It just does not get cold enough for a long amount of time for a Winter pattern. Lots of Texas lakes are like that. BUT, some are not, because of their water depth and depending on the Winter Cold.
So Yes and Yes- the fish (shad) should move to the back of the coves and then move out to the Winter spots but often times we just "slide" from the back of the coves Fall to the Early Spring patterns. Some of the South end lake fish will go deep but they are often times DEEP Water fish anyways.
Is it a SHOCK- Not particularly that strong of a word. It is a "expedited adjustment phase" that they follow for that day or seasonal location shift. This time of the year the fish can be like a bunch of "Vagabond Gypsies", always moving and relocating until a prevalent weather/temp pattern sets in.

Excellent description and reply, Bigron119. Thanks for your knowledge and sharing the info..