You’ve probably heard the saying, “You can find 90 percent of the fish in 10 percent of the water.” From my experiences, I would say that is pretty accurate but understand that the 10 percent of the water where fish are holding in is in a constant state of change.
Venturing out on a lake can be a little overwhelming on where to begin your search.
So pick the lake apart. Find a map and look over the depth contours and locate the areas that look most conducive to holding the fish you are seeking and start there. Fish need food, oxygen, and usually relate to structure or cover. Here are a few factors that provide a starting point for locating fish on your own.
Fish obviously need to eat to survive. Panfish eat bugs, leeches, worms, and small minnows, then predatory fish eat minnows and small fish, and then the largest predators will eat just about anything that fits into their mouth. But they definitely will seek out a particular type of food depending on the season. Look for areas that have the right type of food, and the fish will be nearby.
Oxygen is a no brainer. Fish breathe using their gills to absorb dissolved oxygen from the water. That seems simple enough, but when you investigate further, you will see how fish relate to certain areas of a lake because of oxygen content. Fish will seek depths of the water column that have sufficient oxygen. Many factors including water temperature, weed cover, and depth correlate to determine oxygen content in the water. As water warms, it holds less oxygen. Healthy weeds produce oxygen through photosynthesis, but when weeds get too thick, they’ll start shading out lower weeds, which then die and absorb oxygen as they decompose. That’s why shallow stagnant bays with high water temps and thick weeds hold fewer fish by mid to late summer.
“Lake turnover” and “thermocline” are terms we hear when it comes to locating fish, but you have to understand what they mean. Most lakes turn over twice a year – once in the spring after ice goes out and then again in the fall when surface temps cool to around 50 degrees. Lake turnover means the water from the surface falls to the bottom. All water is mixed together and oxygen is dispersed throughout the water column. After turnover fish can be found in all depths of the lake. Click the link to learn more about turnover (https://www.outdoornews.com/2015/10/08/fishing-tips-catching-fish-around-the-challenging-fall-turnover/
As the summer progresses water temperature rises and more and more weeds die off and sink to the bottom and decay. Decomposition of plants and algae reduce the amount of available oxygen raising the thermocline in the water column. The thermocline is the transition point between warm to cool water, but also the point at which oxygen levels drastically change. Fish won’t spend much time below the thermocline because they don’t have adequate oxygen, and there isn’t much for food down there for the same reason.
Most people can use their sonar units to locate fish, but you also can determine the depth of the thermocline with most units! If you want to find the thermocline, just turn up the sensitivity and drive slowly from shallow water to deep water. The thermocline will appear as a distinct line across your sonar screen; sometimes it can just show up as a
With the sensitivity turned up you can see the thermocline at about 30-feet with some fish suspended above. You will want to turn the sensitivity back down after locating the thermocline to get a more accurate reading of fish and weeds. photos by Jason Revermann
line and other times it will all be shaded below from the thermocline to the bottom depending on the unit. By determining the thermocline you can avoid fishing in water that won’t hold fish.
I’ll often find fish over depths deeper than the thermocline, but they will be suspended in the water column at or above that line. Crappies, walleyes, and northerns will often suspend out in the deeper basins this time of year. Towards evenings these fish will tend to push towards sunken humps and shoreline structure at the similar depths that they were suspending in throughout the day. Good tactics for targeting these suspended fish include lead core trolling, vertical jigging, or a slip bobber with live bait.
Use your electronics to find the thermocline and also to locate fish. Once you locate fish, it’s up to you to turn them into biters.
Good luck fishing and stay safe!