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Paris River Fish Monitoring Annual Report Introduction The lower Paris River, Arizona, is an interesting stream because of its depauperate ichthyofauna. Despite the myriad of non-native fishes that have been captured in or near its confluence with the Colorado River, it commonly contains only two species offish, both of which are native to the stream: flannelmouth sucker Catostomus latipinnis and speckled dace ~ Rhinichthys osculus. This is probably due to the wide range of temperatures that it experiences and the severe flooding that it experiences nearly every year. Despite this, the Paris River is an important spawning stream for these two Colorado River native fishes (Arizona Game and Fish Department 1996a). Flannelmouth sucker use the Paris only seasonally for spawning and early rearing (Weiss 1993; Brouder and Hoffnagle 1997a; Thieme 1997; Weiss et al. 1998). Juvenile flannelmouth suckers will stay in the Paris as long aspossible -usually until a flood flushes them out. Speckled dace may be the only year-round residents of the stream, but their numbers are also susceptible to reduction, at least temporarily, by severe flooding. Spawning of flannelmouth sucker in the Paris River has been documented since the 1970's (Suttkus and Clemmer 1976; Carothers and Minckley 1981; Maddux et al. 1987; Weiss 1993; Thieme 1997). Although eggs andlor larvae have been regularly observed in the Paris River since 1993, no indication of recruitment of these fish into the population had been found prior to the 1996 year class (Weiss 1993; Arizona Game and Fish Department 1996a), which has ~ survived longer than any other recent year class (Brouder and Hoffnagle 1997a; b; Thieme 1997). This was probably due to adrought-induced lack of flooding in the Paris River, which allowed larvae to remain in the warmer Paria, instead of being displaced into the colder Colorado River. In addition, unusually high flows in the mainstem Colorado River created a large, warm pool in the mouth of the Paris which may have provided rearing habitat for yo•~ing- of-the-year (YOY) fishes (Thieme et al. 1997). In 1997, 80 -120 mm total length (TL) flannelmouth suckers were captured in the mouth of the ParisRiver -probably fish from the 1996 Paris River cohort (Brouder and Hoffnagle 1997b). In 1998, a few flannelmouth suckers 200 - 250 mm were caught in the mouth of the Paris, indicating that the 1996 year class maybe • Hofrnagle 1994, Paris River 1998 Armmual Report Arizona Game 6t Fish Depart¢ient 1