Four hundred thirty-three smallmouth bass (Micropterus dolomieui) were collected from ten sites on Crooked Creek in North Central Arkansas from just below the city of Harrison to the White River in the summers of 1988-90. Necropsy of these hosts for yellow grub (Clinostomum marginatum) metacercariae showed a range of mean abundance (average/fish) from 1.4 ±1.9 (SD) at a far up stream site to 105 ± 368 at the White River juncture. An increasing mean abundance of C. marginatum was seen from the uppermost sites of the creek downstream to the White River. Relating stream mileage with mean abundance gave a correlation coefficient (r) of 0.78, with P= <0.01. Maximum abundance (maximum number of parasites in a single host from a site) ranged from 7 to 2500 and also showed a positive correlation with stream mileage (r=0.77,P=<0.01). Prevalence (% fish infected) at the different sites ranged from 61 to 91% but showed no significant correlation with stream distance. The increasingly heavier infections seen in the downstream sites are not due to poor water quality but probably to the combination of the greater presence of the definitive host, the great blue heron, and large intermediate host (smallmouth) populations.

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