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1996 Paria River Native Fish Monitoring refuge/rearing area for YOY flannelrnouth suckers. Larval flannelmouth suckers are prone to drifting out of spawning tributaries upon reaching swim-up stage (Robinson et al. 1996). The slackwater pool, acting as a rearing area for larvae and YOY, allowed flannelmouth sucker to grow to 90 mrn TL by the fall. The slackwater pool provided suitable rearing habitat for long periods of time, increasing their survivability upon entering the cold mainstem Colorado River (Thieme et al. 1996). The lack of flooding from April -early July aiIowed YOY flannelmouth suckers to remain in this rearing area through the summer. By July, fish were large enough to withstand the small spates that occurred during this period. See Thieme (in preparation) for a more thorough description of flannelrnouth sucker population dynamics in the Paria River in ~ 1996. The presence of adult flannelrnouth sucker mortalities upstream in the Paria River are indicative of an upstream spawning tun followed by post-spawning mortality. These data support findings of Suttkus and Clemmer (1976), Carothers and Mmckley (1981) and Maddox et al. (1987), who documented spawning runs up the Pavia River. Weiss (1993) also reported that spawning occurred in 1992 and 1993 throughout the lower 1 d km of the Paris River. However, no previous record of post-spawn mortality has been recorded. Weiss (1993) also noted an increase in the mean length of adult fish between 1992 and 1993, indicating that the Pavia River population of flannelmouth sucker may be becoming senescent. Our results showing adult post- spawning mortality may be further evidence of an aging population. Excellent rearing conditions in the Pavia River in 1996 may provide some recruitment into the adult population. Catches of speckled dace through the year appeared to show adie-off of adults, replaced by YOY later in the summer. The life span of speckled dace is only 2 - 3 years (Mnckley l 973) and decreased catches in mid-summer 1996 may reflect adult mortality. This was followed by the • appearance of YOY being recruited into the population in late July through September. Decreased catches in late October may reflect fish leaving the Pavia River as temperatures dropped below that of the Colorado River. We feel that continued monitoring of the Pavia River and its use by all Gfe stages of flannelmouth sucker and speckled dace is necessary. With low levels of recruitment having been reported by past studies, efforts to quantify post-spawn mortality of an aging adult population of flannelmouth suckers should be continued. Lastly, variables such as Pavia and Colorado River discharges should be taken into account when examining factors affecting successful recruitment. 12 Brooder and Ho$nagle, 1996 Annual Report Arizona Game & Fish Department •