That is a tough question to answer with a real reason based on fact. yes most of the fish will be at the thermocline which is usually around the mid 60's temp and then colder below. In really hot summers which this is not when the surface temps hit 90 in late summer I have caught them down to 40 feet at the prescribed thermocline but that being said they are on the good spots as well at the 25 to 30 foot depths as well. Prior to the alewives, they were always from 25 up no matter what the water temp was until turnover.