In the dead of night, the men would descend upon the country's salmon rivers with brilliantly-burning torches and spears. Stunned by the sudden light, the salmon became easy targets for the spears. Trout are especially good at adapting their vision to changing light levels, which is one reason why they so often feed at dusk and dawn. In low levels of light, their superior sensory systems give them tactical advantages, driving them into confident feeding frenzies. Although fish can distinguish colors, anglers must remember that water affects color.
Blue wavelengths penetrate the deepest into water, whereas reds penetrate the least.
The last color visible to a fish at night is blue, and blue is the first color the fish sees in the morning. The sequence in which the color spectrum disappears from the water at night is red, orange, yellow, green and blue. It reappears with daylight in reverse order. Unlike humans, fish do not have general binocular vision, but they do have nearly complete peripheral coverage in separate visual fields of 180 degrees. They have a narrow field of binocular, stereoscopic vision where their visual fields overlap above and in front of their eyes.