The Best Time to Fish According to the Bass
Like any other visual predator, a bass' hunting ability varies with the photic environment. There isn't an animal alive; neither predator nor prey that is lord and master of the entire light intensity range.
If there is one timeless principle in the world of sensory biology, it is that any given sensory system is built on a series of compromises. In gaining an advantage over its prey in one arena, a predator loses ground in another. Neither predator nor prey can master everything. Survival is a constant game of give and take.
Every fish species is designed to operate best within some established light intensity range, either at one of the two extremes (blinding light or pitch black) or somewhere in between. Bass appear to effectively straddle that fence without being stellar in either direction. A bass' strength lies in its ability to play the middle ground well, especially during the periods of dawn and dusk.
The bass eye is constructed so its large round lens protrudes through each pupil. This protrusion provides the bass with a wide field of view. But it also has the downside of preventing the pupil from opening and closing. The pupil is stuck wide open no matter how intense the ambient light may be. Because bass cannot control their pupils and because they do not have eyelids, they are left to deal with whatever light comes their way.
To some degree that is not as bad as it first seems. Because of water's light absorption properties, it tones down even the bright light of midday. For that reason there is less need underwater for a light intensity regulator such as pupil contraction.
The back of the bass' eye is the key. It contains specialized pigment cells that contain a dark substance called melanin, the same pigment in our human skin for that great tan. It gets pretty complicated inside the eye, but simply put, the melanin pigment cells can change how the eye works in bright and not-so bright conditions.
For daytime, bass are said to have photopic vision; at night and other low light conditions, bass have scotopic vision. These two types of vision are dramatically different. What a bass sees at night is definitely not what it sees during the day.
So what does this mean? Simply, the bass' daytime vision has enhanced depth perception and color identification. In lower light conditions, the bass' eyes take in more light for improved vision when its prey can't see as well.
I guess that's why most of us fish more at dawn and dusk, when the bass is using both vision types.