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because the experts felt that these sampled the different microhabitats used by the species. When a consensus was reached by the experts to use a given 51 curve or to pool data to develop a new curve, the re- sultant curve was regenerated on a com- puter file and presented on a limelite pro- jector for review and final approval. Most 51 curves were fitted as closely as possible to the raw data, except where the experts felt the need to vary the curve fit in order to more closely encompass the raw data or to describe a habitat use not reflected in the raw data. Each 51 curve received a con- fidence rating by the experts (A = high, B = medium, C = low, D = very low), based on the quality of the data, and on how closely it described the habitat use as per- ceived by the experts. The development of category I curves using the Delphi technique did not pro- ceed as expected. The species experts failed to submit category I curves prior to work- shop 2 because they felt that there were no data or observations on these life stages or knowledge of their habitat needs, and therefore, they could not render a profes- sional judgment. For those life stages in which the experts had some knowledge, the category II curves developed for other sympatric species were applied. Although all the 51 curves for this proj- ect were developed from raw data, many were modified by professional judgment, such that the final curves could not be clearly defined as either category I or II. As an example, the depth curve for adult humpback chub was modified to reflect use of deep water habitat because the experts felt that sampling efficiency was limited in deep water. The experts felt that although the curves reflected the raw data (which would classify them as category II), many had been modified, but not sufficiently to justify a category I designation. Thus, the panel of species experts requested no ca- tegorization for the 51 curves developed from this project, although the curves are most closely allied to the category II defi- nition. The experts further concluded, follow- ing an examination of the habitat types from which the microhabitat data were col- lected, that an 51 curve should not be used I~ 36 in current PHAB51M analyses if it met any of the following conditions: (1) 25 percent or more of data from backwaters, concav- ities, isolated pools, embayments and grav- el pits; or (2) 50 percent or more of data from eddies; or (3) 60 percent or more of data from a combination of 1 and 2 above. This general habitat constraint was im- plemented because the species experts felt that the characteristics of habitats identi- fied in conditions 1 and 2 could not pres- ently be simulated. This general habitat constraint applied to 8 of the 18 curve sets developed for the three species, which meant that the species experts recom- mended against use of these curve sets un- til the specified habitats are characterized by simulation models. At the conclusion of workshop 2, the species experts and participants felt that not enough was known about the biology and microhabitat used by the endangered Colorado River fishes to declare the 51 curves from this project as final. Instead, the experts chose to identify these 51 curves as "interim 51 curves," feeling that addi- tional information was being gathered through ongoing research projects. The experts also recognized that other microhabitat parameters besides depth, ve- locity and substrate are likely to be im- portant to the rare fishes of the Colorado River. In this system, for example, cover may not be manifest in the traditional sense of overhanging banks and vegetation as in a montane stream. Rather, it may be de- scribed as turbidity for concealment from predators, lateral structure such as vertical rock walls or talus slopes, or instream structure such as rocks, sand bars, and rock jetties. The experts recognized the need to begin recording cover as a microhabitat pa- rameter for these fish. Task 5: 51 Curve Refinement Following workshop 2, all curve sets identified by expert consensus were re- fined and reissued to the species experts and workshop participants for final ap- proval and comment. Comments were in- corporated into a final report (Valdez et al. 1987), which was distributed to all inter- ested parties. Rivers. Volume 1, Number 1 J an uary 1990 This project result, riverine habitat for 11 Upper Colorado RiVE These were developl identified by the ex mm total length); yo' (21-74 mm); juvenil adults (>260 mm). C ing of depth, veloc curves, was develo}'l no substrate curve \\ vae. Larvae Very little is knl hatched humpback I lieved that larvae use of larval Colorado ! there were substanti. 2). They agreed that t used by larvae of the ably similar, but felt probably use a diffe dicated by the rocky juveniles and adults I teria were develope4 Thus, the depth and plied to larval hum same as those devel Depth, velocity and 1 Parameter Depth (feet) Observations Mean Variance Minimum Maximum Velocity (feet per seeOI Observations Mean Variance Minimum Maximum Dominant substrate" . ND = substrate not 51 = silt, SA = sand, I R. A. Valdez et a1.