Nest Association of Dusky Shiners (Notropis cummingsae) and Redbreast Sunfish (Lepomis auritus), a Potentially Parasitic Relationship

Age-specific habitat segregation and localized migrations to spawning grounds were noted in Notropis cummingsae (dusky shiner) in the Savannah River drainage, South Carolina. Notropis cummingsae spent most of their adult lives associated with noticeable current, usually in scour pools or eddies. Slow, still pools were used for spawning and larval rearing. The young N. cummingsae remained in the pools until juveniles, then joined the adults in faster water. Within pools, N. cummingsae spawned in the nests of Lepomis auritus (redbreast sunfish). The L. auritus defended their nests from N. cummingsae, but the symbionts accessed the nest primarily when the guarding male host was away from the nest or preoccupied with another centrarchid. While on the spawning grounds, N. cummingsae fed voraciously on eggs within the centrarchid nests. Gut content analysis of these N. cummingsae indicated that they ate almost exclusively centrarchid eggs/larvae even though eggs/larvae of both species were in the nest. A mean of up to 9.2 larvae was eaten per N. cummingsae, and from 15 to over 100 individuals were observed in a nest at one time. Predation of eggs/larvae by N. cummingsae appears to reduce the reproductive success of the host, resulting in a parasitic nest association, but more detailed research is necessary to determine this unequivocally.