Parasite Community Structure in Pimephales promelas (Pisces: Cyprinidae) from Two Converging Streams

Parasites of the fathead minnow, Pimephales promelas, were examined in fish collected from Elk Creek (40.88534°N, 96.83366°W) and West Oak Creek (40.90821°N, 96.81432°W), Lancaster County, Nebraska. These 2 streams are part of the Salt Valley watershed and flow together approximately 2 km downstream from the collection sites to form Oak Creek. This study examined the extent to which the 2 tributaries constitute a continuous habitat with respect to fish hosts. The parasite community included Trichodina sp., Myxobolus sp., Dactylogyrus simplex, D. bychowskyi, and D. pectenatus (all on gills); Gyrodactylus hoffmani (gill and body surface); Posthodiplostomum sp. (neascus, body cavity); and Uvulifer ambloplitis (encysted in skin). Among 46 fish from Elk Creek and 56 fish from West Oak Creek taken on 5 dates during April–July 1998, U. ambloplitis was found in Elk Creek fish at prevalences of 44–100% but in only 2 West Oak fish on 1 date. Prevalence and mean abundance of D. simplex also differed between the 2 sites. On the basis of these observations, fish populations in the 2 streams were considered to be distinct, with little or no fish movement between the tributaries.