Data Collection Report - Flood Control District of Maricopa County

Range: Breeds locally along the Colorado River’s confluencewith the Little Colorado River, the headwaters of theLittle Colorado River near Greer and Eager, south ofYuma, the middle Gila, Salt, and Verde rivers, the middleto lower San Pedro River, and the upper San FranciscoRiver near Alpine (AGFD 1997e).Residence: Arrive in late April and begins to nest in late May(Phillips, Marshall and Monson 1964, Unitt 1987).Migrates south in August and September (AGFD 1997e).Assessment: Southwestern willow flycatcher may occur regularly insuitable habitat (dense riparian woodland) within theproject area along the Salt and Agua Fria rivers. Surveysare recommended to determine presence or absence priorto development activities within such communities.Razorback Sucker (Xyrauchen texanus)Status: Listed endangered with critical habitat designated inMaricopa County at Horseshoe Lake.Habitat: Slow backwaters of medium and large streams andrivers, and impoundments at least 1 m deep over sand,mud, or gravel substrates at low to intermediateelevations (AGFD 1995a).Diet: Insect larvae, plankton, algae, and detritus (AGFD1995a).Range: Small, isolated populations exist in the lower ColoradoRiver south of Lake Havasu (FWS 1998), and inHorseshoe Reservoir in Maricopa County (SeeAppendix).Residence: Permanent.Assessment: Razorback sucker is extremely unlikely to occur in theproject area, chiefly because the species is rare, and theadverse impacts known to exist by exotic fishes on nativefishes. Reintroductions into the Gila and Salt rivers haveapparently failed and are currently ongoing only in theVerde River. Populations are known to occur only in theVerde and Colorado rivers.Gila Topminnow (Poeciliopsis occidentalis occidentalis)Status: Listed endangered without designated critical habitat.Habitat: Springs, cienegas, and streams below 4,500 to 5,000 feetin elevation (FWS 1998, AGFD 1995b).Diet: Crustaceans, insect larvae, and detritus (AGFD 1995b).Range: Historically found throughout the Gila River drainage,but now restricted to the Santa Cruz River and itstributaries (FWS 1998). Within the Gila River basin,Gila topminnow occurred in the Gila, Salt, Santa Cruz,San Pedro, and San Carlos rivers, and their tributaries.They were never documented to occur in the Verde,Hassayampa, or Agua Fria rivers. Ten locations withinthe Gila River drainage are currently known to supportGila topminnow. However, this species has not beenrecently observed in the Gila, Hassayampa, or Coloradorivers (Weedman and Young 1997, AGFD 1995b). Nonatural populations exist in Maricopa County (FWS1998).Residence: Permanent.Assessment: Gila topminnow is extremely unlikely to occur in theproject area, which is outside the existing known range.However, a possible reintroduction site has beenidentified at the Tres Rios project (personalcommunication, Roland Wass, City of Phoenix WaterServices Department, 12-20-99). This potentialreintroduction should be monitored prior to commencingany construction activities at or downstream of this site.Desert Pupfish (Cyprinodon macularius)Status: Listed endangered with critical habitat designated atQuitobaquito Spring in Pima County.Habitat: Historically occurred in springs, marshes, backwaters,and tributaries from sea level to approximately 5,000 feetelevation (FWS 1998, AGFD 1994).Diet: Insects, crustaceans, and plants (AGFD 1994).Range: Historically occurred in the San Pedro, Santa Cruz, andlower Gila rivers, and lower Colorado River drainages inArizona (FWS 1998). Currently, one natural populationof C. m. eremus exists at Quitobaquito Spring in OrganPipe National Monument, and no natural populations ofC. m. macularius exist in Arizona (Weedman and Young1997, AGFD 1994). Recent and current reintroductionsof the latter subspecies occurred in Pima, Pinal,Maricopa, La Paz, Graham, Cochise, and Yavapaicounties (FWS 1998), but only one population at ColdSprings remains extant (Weedman and Young 1997).The reintroductions may have contained a mixture ofvarious subspecies, which potentially invalidates thegenetic integrity of either natural subspecies, andobscures the reintroduction history of this species inArizona (Weedman and Young 1997). No natural orDIBBLE & ASSOCIATES 41 DURANGO ADMPDATA COLLECTION REPORT