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Pla!ania, Dudley, and Maruca. 2000. Drift of Fishes In the San Juan River 1991-1997. FINAt. C") (""-) ..... ...... Q above 10,000 cf.~; and negatively correlated with number of days less than 1,000 cfs (Figure 17). At Mexican Hat, mean annual CPUE was positively correlated with number of days greater than 5,000 cfs (Figure 18), while maximum daily CPUE was positively and strongly (r ,0.98 for both) correlated with number of days with discharge greater than 8,000 cfs and 10,000 cfs (Figure 19). ~ Relationship oj Daily Drift CPUE and Daily Flow by Year and Site Information on CPUE of fishes was not available for 1991 at the Four Comers site. During 19-25 July 1991 and 29 July-5 August 1991 the rwo largest samples (n=193 and n=622, respectively) of red shiner were collected (Figure 20). Moderate increases in stream flow corresponded to these collections. During 1992, there was a modest spring runoff and severa/large summer rainstorms that resulted in considerable increases in stream flow. No red shiner were collected at the Mexican Hat coIlecting locality in 1992 and there were two very minor pulses of drifting larval red shiner at the Four Corners site that followed summer 1992 rainstorm events. CoIlections of red shiner in 1993 were also relatively low at both sites but again corresponded to increased stream flows caused by small summer rainstonns. When rainstorm events that resulted in increased catch were removed from the dataset (Figure 21), it was apparent that very few larval red shiner drifted during non- rainstonn periods. Several August] 995 rainstorms yielded shght increases in stream-flow, notable increases in instream debris levels, and nearly all (99.3%) drifting red shiner collected during that year. The early August rainstorms were small and resulted in minor increases in flow, but markedly increased levels of suspended sediments in the water column. The largest collection of drifting red shiner was taken in 1995 at Mexican Hat after a small rainstorm. Despite the low t10w experienced in 1996, there were collections of drifting red shiner made in late summer during and following very minor rain events. A moderate number of red shiner (28.9%) were collected during non-rainstorm periods. There were few larval red shiner collected in 1997 immediately after mid-summer rainstorms. The timing and pattern of coIlections of fathead minnow were similar to those observed for red shiner; most of the fish were collected during or after rainstorms (Figure 22) as opposed to non- rainstorm periods (Figure 23). The highest numbers of fathead minnow collected were taken in 1991 during the same two rainstorm events (19-25 Jnly; n=14 and 29 July-5 August; n=45) that yielded large nnmbers of red shiner. Collections of larval fathead minnow were relatively consistent in magnitude at the Four Comers sampling locality in 1992, 1995, 1996, and 1997. During each of those years, all drifting larval fathead minnow occurred following summer rainstorms. Few individuals were taken in 1993 at Four Comers, but most (97.8%) were associated with rain events. Very few fathead minnow were capOlred in drift-nets at the Mexican Hat site in 1991, 1992, or 1993. The few individnals taken in 1995 followed minor increases in flow. The greatest density of fathead minnow at Mexican Hat occurred in 1996 foIlowing a summer (mid-July) rainstorm. There were no drifting individuals of this species capOlred at Mexican Hat in 1997. Nearly all speckled dace at Four Comers in 1991 were taken during three rainstorms (9-15 July, n~13; 19-25 Jn1y, n=81; and 29 July-5 August, n=90) (Figure 24). This mirrored the pattern exhibited by red shiner and fathead minnow with the exception of the earlier capture of drifting larval speckled dace. A few drifting speckled dace were captured in drift-nets at Four Comers in 1992 following two July rain events; no individuals were taken during non-rainstorm periods (Figure 25). Very few speckled dace were coIlected at Mexican Hat in either 1991 or 1992. A large pulse of drifting speckled dace (n=304) was coIlected from 3-6 July 1993 at Mexican Hat during a period of increased flow (and debris Icvels). Sampling at the Four Comers station began on 6 July 1993 and speckled dace were collected there during non-rainstorm periods (34.6%) prior to several small August rains that apparently triggered increased drifting. Speckled dace were capturcd in drift-nets throughout 1995 at both sites but Four Comers prodnced many more individuals than Mexican Hat. Peaks in abundance at both sampling localities were recorded during and shortly after local rainstorm 34