thermocline in deep rivers

[rich c]

New here not sure if I am posting in the correct thread. In an earlier thread they were disscusing thermoclines in Pa. rivers My question is do thermoclines set up in rivers with deep spots up to 200' such as the St. Lawerance river, and how would that effect fishing ? Thanks rc .Or maybe someone could tell me where I might find this information. I know that below the thermocline in summer the water is oxygen poor and in the winter the opposit is true. I guess my real question is do thermoclines set up in rivers with these depths. 60' 100' even 200'. would appriciate any help with this you might give.