Glasgow Daily Times, Glasgow, KY


August 31, 2012

Ideal conditions

Temperature, oxygen content key factors in fishing

GLASGOW — In this article we will attempt to answer the most-asked question among anglers: “Where are the fish?”

A tall order you say? True, if we attempt to do so with maps or directions to the hottest spots on lakes within a 100-mile radius of your specific location.

But that’s not the way we’ll be dealing with the question. Our approach is better. It deals with principals and will better enable you to effectively locate fish anywhere you fish.

To begin with, you need to understand that on any given lake or pond, 90 percent of the catchable fish will likely be concentrated in only 10 percent of the available water... maybe less. To complicate matters, that 10 percent area will change from season to season.

The first thing we must understand is that fish are cold-blooded creatures; their body temperature being regulated by the temperature of their environment.  Since fish have virtually no control over their body temperature, in order to function, they must seek out areas of favorable temperatures. We’ll call them “comfort zones.”

But now we are faced with another problem. Not only will temperature affect the location of fish, but available oxygen will as well. Of the two, oxygen is far more important and will even force fish into lower or higher temperatures than those preferred.

Considering both factors through a 12-month period, temperature is the ruling factor during the colder months of the year, while oxygen content is most important when trying to determine locations during the hotter summer months.

In the summer, the sun heats the upper depths of the lake, creating a narrow band of water below the surface called the “thermocline.” Above the thermocline the water is warmer, but also has the best oxygen content. Below the thermocline, the temperature drops sharply, but so does available dissolved oxygen. In most situations, that makes the thermocline area itself the most comfortable zone for fish.

Find the thermocline and you’ll find fish, especially if it is located at the same level as a channel break or other structure the fish can relate to. Modern sonar units will display thermoclines. If you don’t have one, fish breaks and structure in the 12-16 foot range on average, deeper if you are fishing a very clear lake.

One exception to this rule is those shallow shoreline areas that are shaded and have heavy vegetation. These areas will have high dissolved oxygen content and may be several degrees cooler that adjacent open water.

It’s a different story when fishing the colder months of the year. As the surface water cools in late fall, it becomes more dense and sinks, causing the warmer (less dense) water at the bottom of the lake to rise, resulting in what is called the “turnover” where the water in the lake actually turns over. In the process, the entire lake takes on good oxygen content and that’s when temperature becomes the ruling factor. Since there is available dissolved oxygen throughout the water table, fish will seek out the most favorable temperature according to depth.

Finding active fish isn’t always an easy process. And at some times of the year, it’s even harder than others.

But the process becomes a lot simpler when you understand that temperature and oxygen play critical roles in where fish will be... and where they won’t be.


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Barren County vs. Glasgow