Changing seasons – stratification and the turnover

Fall is here. Temperatures are dropping. The first cold fronts slide through but don’t stick around long. It’s a great time to fish. No bugs. No jet-skiers. Your hunting buddies are in the woods so you may have the lake to yourself.

But the bite is off. What’s going on? A question we hear in the fall when fishing gets slow is “what is this thermocline everyone talks about, and what does it mean when the lake turns over?”

Here is a little limnology lesson. Let’s start last winter to see how we get to the fall turnover. 

Water reaches its maximum density at 38˚F so the deepest water may be the warmest. Oxygen is plentiful and bass metabolism is slower so they don’t need to feed as often. Temperatures can be fairly uniform so they can live almost anywhere — but they will usually seek out the warmest water in their home range. Smallmouth will typically travel longer distances to find wintering areas than largemouth. Large schools of bass will often congregate in relatively small areas this time of year.