McFarland, W.N., and E.R. Lowe. 1983. Wave produced changes in underwater light and their relations to vision. Environmental Biology of Fish 8. 173-184.

Study Objective: Exploring the relationships between the spatial and temporal characteristics of vision and light changes to wave-induced light changes in aquatic environments.

Methods: Review of light and vision concepts as they might relate to aquatic habitat characteristics.

Summary and Conclusions: 1) spatial and temporal frequency responses of animals with image-forming eyes are qualitatively similar to humans; 2) contrast sensitivity is maximal at intermediate levels of detail; 3) the spatio-temporal frequencies at which contrast sensitivity is maximal vary in different species and, probably, represent adaptations to detect objects relevant to each species life-style suggesting that the evolution of image-forming vision in invertebrates and vertebrates was influenced by the same selective force; 4) flicker rates from surface waves acting as lenses focusing sunlight beneath the surface match the frequency responses of animals with image forming eyes suggesting that invertebrates and vertebrates visual systems evolved to function in the time-frame set by wave-induced flicker in shallow seas; 5) dorsal patterns and bars on many fish probably relate to wave induced fluctuating frequency patterns.

Comments: Underwater, patterns of light and dark cast by flickering light cause small objects to merge into the flickering glare of the surface when viewed from below. These same objects when viewed from above or the side against a non-flickering background, such as a shallow bottom, tend to flash into view. This vision component could be part of why young zooplankton-feeding salmon select epibenthic zooplankton in shallow water.