Fishing the thermocline intersect on Lake Ontario can be one of the most effective ways to target trout and salmon. In this post, we will discuss the methods we use on our Lake Ontario Charters in Oswego, New York. So, let’s get started!


Perhaps first, lets define what a thermocline is. A thermocline is where two different temperature bodies of water meet below the surface. A thermocline intersect is where the preferred temperature of our target species meets the bottom of the lake bed or substrate. We will be referring to thermocline intersect throughout this article!

fishing the thermocline intersect for big browns like this

Preferred Temperatures

We first need to decide which species we wish to target with this method. For all intents and purposes, we will look at brown trout, king salmon, and lake trout. Each has their own preferred temperature range in which they like to inhabit. Lake trout prefer 42 degree water while kings like 44 degrees. Last, but not least, brown trout prefer 55 degree water.

Find The Right Depths

The key is to find out where these temperatures are located in the water column on any given day. We love the Fishhawk X4D for this purpose. By lowering the probe down into the water column you should be able to locate the preferred temperature your looking for based upon specie target. For instance, lets take brown trout.

Use It For Browns

Our Fishhawk tells us that 55 degree water is located down 60 feet in the column. We would then troll into 60 feet of water and fish near the bottom and above to target the browns. Sometimes you will see them at or near the bottom of your graph giving you confirmation. Before I give up fishing 60 feet for browns, I would troll plus or minus 10 feet of depth and continue to parallel the shoreline first.

Where To Find Lakers

Lake trout are pretty much the same as browns in that they most times like to relate to the bottom. When the Lake sets up, lakers can be found in deeper water hugging the bottom in 42 degree water. Even though you could put your probe down there, we usually don’t for fear of losing it by snagging bottom. Instead, we uses our graph to locate them. Be advised that when water temperatures of 42 degrees are up off the bottom and stratified, lakers can be found there quite frequently. Spring lakers can sometimes be found close to the surface.

Apply It To Kings

Fishing the thermocline intersect for king salmon tends to be seasonal in nature. As the spawning time draws near, kings will usually hug the bottom where 44 degree temperatures meet it. Again, using an X4D dials you in to where in the column that 44 degree water is. Besides staging time, there will be other instances where kings will hug the bottom. This is especially true when their preferred temperature gets found deep in the water column. This is also true after a huge west wind blow on our end of the Lake.

Nothing is a 100% true all the time when it comes to fishing. There will always be exceptions to the rule. But, if what your doing just ain’t working, trolling the thermocline intersect can save the day. Some days it’s the Achilles heel for Lakers, browns , and king salmon.

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