Coexistence and resource partitioning in two species of darters (Percidae), Etheostoma nigrum and Percina maculata

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Abstract
This study investigated partitioning of resources along the dimensions of space, food, and time by johnny darters (Etheostoma nigrum) and blackside darters (Percina maculata). Although both species were abundant in the midcourse of the Whitemouth River and occurred together in all habitats, space was partitioned on a vertical basis. Johnny darters were exclusively benthic whereas blackside darters were much less restricted to the bottom. The latter retained a well developed swim bladder permitting use of the vertical component of the environment. Partitioning of food resources occurred and although similar taxa were consumed by both species (aquatic insects and Crustacea) the proportions were not similar. Johnny darters fed mainly on benthic items whereas blackside darters ate pelagic items. Differences in protrusibility of premaxilla, position of the mouth and eyes, retinal acuity, and number and morphology of gill rakers reflected different modes of life. There was no evidence of partitioning by time.