Weed shiners are listed as endangered in Iowa. In the spring of 1990, one weed shiner (Notropis texanus) was collected from the Crooked Slough Complex, Pool 13 (river mile 554.3) of the Upper Mississippi River System. Prior to this study, there is no record of weed shiners collected in Pool 13. After the initial collection, a follow-up search for weed shiners was undertaken during fall 1990, and during late summer and fall 1991, to estimate relative abundance at this site. The Crooked Slough collection site was seined on three separate occasions, and 1,840 fish were collected. No additional weed shiners were captured. Therefore, the collection efforts do not support the hypothesis that the Crooked Slough collection site contains critical habitat for weed shiners or a viable population of weed shiners. Collection of the single specimen during the spring of 1990 suggests that abundance of weed shiners is low at this site.