Get out there before grass dies out is for sure the best bet. Many people say wait a few days-weeks for fish to adjust. When drowned bugs, mice, etc flow into this new water, they wont wait. I have caught fish on a lake that went up 14 feet in three days, fished it the day after it filled up, and caught some nice ones right in the flooded grass. Fish dont wait cause by then the bugs and stuff will be gone, and so I always say neither should us fisherman.