Red-
I dont have info on the broader timing question, but it would make sense that the larger ones can/would spawn earlier. Cant remember where I read it but studies have shown that larger ones internal temps can be something like 5 degrees warmer than the water (vs smaller ones at parity to the water) because they have better internal temp regulation (presumably due to higher body mass to surface area- thus they loose internally generated heat slower). I would bet that the water temp is only a predictor of spawning time to the extent that it influences their internal temps.