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upper end of occupied habitat and proceeded downstream, sampling the first backwater they located in each five-mile reach. Early investigations also included seining habitats adjacent to the sampled backwaters. However, the program was soon standardized to sample only backwaters because it was assumed that changes in numbers within backwaters also reflected changes in other habitats. The Biological Subcommittee used this annual inventory as the basis for the post-larval Colorado squawfish portion of ISMP. The Biological Subcommittee utilized the four important nursery habitat areas in the Green and Colorado rivers for the post-larval portion of ISMP (Table 1; Figure 1). The states of Utah and Colorado were given primary responsibility for sampling reaches within their borders. The Service and Bureau would provide support when necessary. Each reach was divided into five-mile subreaches which formed the basis for the sampling-design. The sampling crew began at the top of the reach and traveled downstream until it reached a backwater which it sampled with a 1/8-inch-mesh seine. Two non-overlapping seine hauls were taken in the backwater. Effort was recorded as area swept by the seine. Colorado squawfish were measured, counted, and released alive if they were large enough to be reliably identified. All remaining fish in the first sample were preserved for later identification in the laboratory to check for Colorado squawfish too small to be identified in the field. The investigators then proceeded downstream to the next backwater which was also sampled with two non-overlapping seine hauls. Colorado squawfish were measured, counted, and released alive. No fish from the second backwater were preserved. The investigators then proceeded downstream to the top of the next five-mile reach before sampling again. Samples were not taken within a five-mile reach if no backwaters meeting ISMP's criteria were found. To ensure that sampling would be consistent among the many investigators who would participate in ISMP, a handbook was developed that outlined the sampling program in considerable detail (USFWS 1987). Standard data forms, encoding instructions, and a database management system were also developed. The relative density, or catch per effort (CPE), of post-larval Colorado squawfish was determined by the number collected per area of backwater swept with the seine. CPE for each reach was calculated as the mean of all seine hauls taken within the reach. Because of the relatively low number of Colorado squawfish collected every year, the data are not normally distributed--an assumption required by many data analysis techniques. McAda (1989) investigated several methods of data analysis for the monitoring program and suggested using geometric-mean CPE rather than the more standard calculation of arithmetic mean. The geometric mean is calculated by using a log transformation (lo&(CPE + 1)) on individual seine hauls before calculating the mean. The mean of the log values is then transformed back to a standard value. A log transformation improves the normality of CPE 2 1 1 1 i