The factor that is most responsible for controlling bass behavior is temperature. Most anglers pay attention to rising or falling water temperature, nothing wrong with that. Water temperature regulates how active bass are and how often they feed. That is only part of the puzzle, however. It is the relationship of air (mass) temperature and water temperature that is the key to predicting daily bass behavior. These two temperature ranges really control bass activity, or lack of it. The following examples will illustrate the importance of this ever changing marriage of numbers.
Most anglers would agree that 55f water is a favorable water temperature for fish activity, certainly for smallmouth and spotted bass. Assuming the AIR temperature has been constant (spring or fall), fishing should be reasonable good. In either season if conditions provide a 3 or 4 day warming trend with surface temperatures rising to 58f in the afternoon, and the nights are not too cold (warm air mass), fishing should break wide open. Conversely, if the afternoon water temperature in April slowly drop from 58f to 55f because of a major cold front, you will find a very tough bite, though the water is 55f. Remember, nights are longer than days in the spring and fall. This is why our lakes took so long to warm this spring. The long, cold nights simply overwhelmed any warming that occurred in daylight hours.
Looking at a summer example, if the water at Clear Lake in August is 78f and the air mass over Northern California is very warm and stable, the morning, evening and night fishing is usually very good. If a major cooling trend sets in, two things will happen. Cool air from the ocean is brought inland by strong winds which usually makes boating on Clear Lake an adventure! While we humans may love the relief from 100f daytime temperatures, bass DO NOT! Though the water temperature may only drop a degree or two, the colder, moist air mass WILL slow feeding activity, particularly for large bass. I have many, many trips under my belt to verify this. If you can, hold off your trip to Clear Lake (or the Delta) until the warming trend begins again.
Two recent night trips to Lake Amador will illustrate how this dual temperature thing works. My first guided trip produced eight bass to 61/2 lbs. The water temperature was 62f and the night air was pleasant. Conditions were perfect for large fish to feed. A week later the water reached 66f which should have found the fish even more active. But a front moved in, causing a cold, damp night. We still caught eight bass, but they were smaller, and the large bass was only 4 lbs. The water temperature was a positive, but the air temperature was an over ruling negative.
Finally, two recent guides to Lake Oroville will reveal how anglers need to adjust their game plan to fit the current weather conditions. One trip last month (May) found 61f water and a rare warm afternoon. I smelled topwater time and we caught seven spotted bass to 3 lbs 5 oz. Six of them were over the 15″ slot. We also caught fifteen on Magic Worms down to fifteen feet. Ten days later, I guided three people at the same spot with the water temperature now at 63f. However, we were fishing the afternoon with our jackets on during a major cold front. The bass were still biting on Magic Worms (6 inch), we caught 35 in six hours! The fish had dropped to the 20 to 25 foot range. They WOULD NOT look at our Storm Chug Bug topwater lures..
So, regardless of the time of year and the water temperature, keep your eye on the weather – and the thermometer! If you have flexibility in your schedule, plan your trip during a warming trend, or at least during stable weather. Then match your baits to the water temperature, and your rewards may be awesome!