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T~ble I. Origin and status of fish species encountered in the Colorado and Green rivers in and adjacent to Canyonlands National Park, 1985-1988. Statusb Origina State Federal Common name (Species code) Family Clupeldae: herrings Dorosoma petenense threadfin shad (TS) NN Family Cyprinidae: carps and minnows Cyprinella lutrensis red shiner (RS) NN Cyprinus carpio common carp (CP) EX Gila atraria Utah chub (UC) NN Gila cypha humpback chub (HB) EN Gila elegans bony tail (BT) EN Gila robusta roundtail chub (RT) EN Gila sp. unidentified chub (CH) Hybognathus hankinsoni brassy minnow (BM) Notropis stramineus sand shiner (SS) Pimephales promelas fathead minnow (FH) Ptychocheilus lucius Colorado squawfish (CS) Rhinichthys osculus speckled dace (SD) Family Catostomldae: suckers Catostomus commersoni while sucker (WS) NN Catostomus discobolus bluehead sucker (BH) NA Catostomus latipinnis flannelmouth sucker (FM) EN Xyrauchen texanus razorback sucker (RZ) EN Family Ictaluridae: bullheads and catnshes black bullhead (BB) NN channel catfish (CC) NN Family Esocidae: pikes northern pike (NP) Scientific name Ameiurus melas /ctalurus punctatus Esox lucius NN Family Salmonldae: trout Oncorhynchus lIIykiss rainbow trout (RB) NN GF Oncorhynchus nerka kokanee salmon (KS) NN GF Salmo trulta brown trout (BR) EX GF Family Cyprinodonlidae: klllifishes Fundulus zebrinus plains killifish (PK) NN NG Family Poeclllldae Galllbusia affinis western mosquitofish (GA) NN NG Family Perclchthyldae: temperate basses Morone saxatilis striped bass (SB) NN GF Family Cenlrarchldae: sunnshes upomis cyanellus green sunfish (GS) NN NG upomis macrochirus bluegill (BG) NN GF Micropterus dolomieu smallmouth bass (SM) NN GF Micropterus salmoides largemouth bass (LG) NN GF Pomoxis nigromaculatus black crappie (BC) NN GF Table 1. Contin/led. Common name (Species code) Statusb Origin' State Federal Scientific name NG Family Percldae: perches Stizostedion vitreum walleye (WE) NN GF · EN = endemic, indigenous \0 basin; EX = exotic, from another continent. NA = native originated in basin; NN = nonnative, from another North American basin. ' . b C2= candidate, category 2; ED = endangered; OF = game or sport fish; NO = nongame fish; TII = threatened. NG NG NG ED ED TH ED ED C2 Distribution and Abundance of Native Species NN NN NN EN NA Colorado Squawfish Colorado squawfish were found in all five regions of the study area (Table 2). A total of 4,348 individuals were captured, including 385 larvae, 3,776 age-O (young-of-year), 175 juveniles (preadults), and 12 adults. The greatest number of larvae were captured in region I (266), with far fewer in regions 2 (I), 3 (37), 4 (60), and 5 (21). Most age-O Colorado squawfish were captured in region I (2,132) and region 4 (1,149), with fewer from regions 2 (50), 3 (355), and 5 (90). All larval and age-O Colorado squawfish were captured in backwaters and shallow, low-velocity shoreline habitats. Of 3,144 larvae and age-a seined-mostly from backwaters-the highest calch rates of 61.9/100 m2 in 1986 and 71.6 in 1987 were from region I (Table 3). The relatively high number of age-a and high catch rate (31.6/100 m2) in region 4 in 1988 were allributed to a large rain-induced flood in the lower Green River that transported large numbers of squawfish into Cataract Can- yon. The lower Green River and Cataract Canyon were coincidentally sampled before and after the rain storm to confirm these observations. Of 175 juvenile Colorado squawfish, the greatest number (65) was captured in region I, while fewer individuals were caught in regions 2 (32), 3 (36), 4 (38), and 5 (4). Juveniles were found in a variety of habitats, but the majority were captured with seines in backwaters associated with sand beaches and along talus-scree shorelines. The rest were captured with electrolishing and experimental gill nets near talus-scree shorelines. Five adult Colorado squawfish were captured in region 4; fewer were captured in regions I (l), 2 (l), 3 (3), and 5 (2). Eight of the 12 adults were captured with electrofishing gear from tamarisk-willow and talus-scree shore- lines, while 4 were captured with gill or trammel nets in eddies near talus-scree. The 12 fish averaged 519 mm TL (range of 425-662 mm TL) and 1,002 g body weight (range of 540-2,043 g). The ages of the adults and juveniles were not determined. Two adult Colorado squawfish, captured in 1986, had been previously caught upstream of Cataract Canyon by the U.S. Fish and Wildlife Service NO NG NG ED NO ED NG NG NG ED C2 ED NO GF OF