From experience, Sunny, Clear Sky’s, little or no wind, tell us not all but most bass are either, on or near the bottom, or within cover, and/or at a depth or place where light penetration is less. When clouds approach, many fish including prey rise in the water column to one degree or another, suspend in the water column, or gradually approach the edges of cover from the inside out. Evidence for this is found in part when we see that calm water surfaces bites occur best in low light especially early and late in the day.
Bass eyes use rods and cones are much like humans. Like you and me, Bass cannot adjust their pupils to varying levels of light quickly. Think about the old Navy Submarine Movies you have seen where the U-Boat surfaces at night and the lights in the sub are changed from white to red for some time before the outer hatch is opened and crewmen go above. They did that change to have their eyes adjust quickly to the dark. Other species of fish are more or less sensitive to light change. Walleyes for example are probably the most sensitive to light. So, in fact, we have to adjust our hindsight to their eye sight. Depth, Overcast Skies, Clarity of water, extent of Chop on the surface, Early/Late in the day, Night, angle of the Sun by season, even Ice cover and it’s thickness, and more, all come into play for them and you.
Biologists have found bass take as much as 15-20 minutes to adjust to changing light conditions. If Bass are positioned in darker places before the darker parts of the storm gets to them, little or no adjustment at all is needed. Some smaller prey fish species take longer than bass to adjust to abrupt low light conditions; giving bass an advantage; heightening search and capture effectiveness.
If hungry fish are found more on the move, higher off the bottom, more near the surface and/or at the edges of structure or cover during those dark times, they are camouflaged there to have a better sight and vibration advantage at capturing prey. Prey fish are there because low light hides their movement. That and the prey also are conditioned to know the flow of food elements (plankton or what have you) is increased; more on the move laterally and vertically. The longer the sky stays dark, the more predator/prey directional movement occurs. With a natural need to use penetrating light to photosynthesize, plankton, rise upward in the water column with darker skies– plankton then sink with brighter skies – plankton eaters (bait fish and most minnows otherwise) follow the source of their food.
If we are good enough anglers to know where our target fish are during times of plenty, and what happens when some cold front moves through, we are then able to pinpoint objective spots to fish. Knowing the average time, it takes for conditions to get back to “normal” we then can pick out the areas and depth levels to explore and increase our catch.
RjZ – Richard Ziert