Fish are cold blooded animals and as such their body temperature changes as the water surrounding them changes. Every species of fish has a water temperature that they are most comfortable in, meaning that their body functions properly at around that temperature. The comfort range for every fish varies around this absolute temperature and is normally expressed as a range of temperatures spanning from 10 to 15 degrees.
The comfort zones or preferred temperature ranges for many pf the popular species of fish are shown on the chart above. If you are fishing and the water temperature is within these ranges for the fish that you are after, you can expect the fish to behave as they have in the past. If however the water temperature is significantly higher or lower than these boundaries, the fish will be more difficult to catch because they are going to be doing things hat they normally do not do to regain their comfort zone. In the summer months many fish that are normally found in shallow water will retreat to deeper water because that water is cooler there. Many species of fish like bass will move to shady areas where the water is a little cooler, like under docks, bridges of underwater structure like stumps and brush.
Remember that the temperature that boat equipment normally reads is the surface temperature and for every 10 feet of depth, there is a temperature drop of about 2 degrees.. If the weather continues to be hot, like it has been this year, the schools of bait fish that would normally hang around in small coves and channels, will also move into deep water because a couple degrees cooler water is very important to these small fish. If the bait schools go deep, the predator fish will follow. So on these hot days, fish deeper for more success.
