Within this study, fish of two ecosystems are investigated: 1) shallow water fishes in waters located in proximity to Duluth-Superior Harbor and 2) open water fishes. Investigation of the former includes a comparison of the invasive round goby to the logperch and black bullhead to surmise any physiological visual advantage for the intruding species. The latter investigation compares the siscowet, kiyi, and deepwater sculpin visual sensitivity to the downwelling light available at depth. Electroretinography was used to formulate spectral sensitivity curves for interspecific comparison. In both studies, fish visual sensitivity matched that of downwelling light available in the respective environments. Logperch showed greater visual depth than the round goby. Siscowet and kiyi visual depth profiles overlapped and deepwater sculpin retained vision at greater depths. Diurnal vision for all species is possible in shallow depths but it is likely that deepwater fishes rely on other sensory modalities during most predator-prey interactions.