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ISMP backwater sampling evaluation <br />estimates of species richness if one of the sampling passes was by seining. In backwaters where <br />capture-recapture sampling targeted centrarchid abundance estimates, abundance estimates for <br />non-centrarchid species were not computed. <br />Backwater length and five widths were measured to estimate backwater area. Mean <br />backwater depth was estimated from three depth measurements obtained at each of three <br />transects. Habitat characteristics such as presence of woody debris, deep water, undercut banks, <br />overhanging or submerged vegetation, and substrate were described for each backwater. Those <br />characteristics were used to assign a score of 1, 2, or 3, which represented an index of habitat <br />quality ranging from simple to complex. <br />In addition to autumn sampling, eight backwaters were sampled in spring of 1998 in <br />order to fulfill the obligation of removing fish from as many backwaters as possible. <br />Backwaters were sampled by seining or electrofishing with enough effort to encompass the <br />surface area once. All fishes were placed in a live basket, native fish were enumerated and <br />released, and non-natives were preserved for identification and enumeration in the laboratory. <br />Six of the eight backwaters had been sampled the previous autumn. <br />Presence/absence and abundance estimation analyses and comparisons <br />A main goal of comparing presence/absence estimates derived from low effort ISMP <br />sampling and higher effort DMR sampling was to determine if ISMP estimates were biased. <br />This was accomplished by comparing the number of backwaters where a particular species was( <br />detected by ISMP sampling to the number of backwaters where it was detected by DMR <br />sampling. If ISMP sampling was unbiased, the expectation was that each technique would detect <br />-5-