I don't think there's less fish, just less biting fish. I heard Cornell talk earlier this week - good news with the gobies is that this years walleye hatch it growing faster than ever feeding on immature gobbies, eventually that will mean more fish, unfortunately they'll be full and won't bite. They said catch rate for walleye is down about 50% even bass catch is down over 30%.
I fished last Sat am and tried to get on the fish I found the previous week but they had moved on, spent over 4 hours and could only put one bass in the boat - only bite I had. In the past I've done better in August fishing after dark, maybe I'll try that next time out.