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320 RAZORBACK SUCKER SPAWNING the historic habitat, the establishmenC of over 30 species of nonnative fishes has permanently altered the ichthyofaunal composition (Tyus et al. 1982). Methods Movement patterns and spawning fidelity of ra- zorback suckers were assessed by two methods: monitoring specific individuals with radio telem- etry and analysis of razorback sucker mark-re- capture data collected between 1975 and 1992. Between 30 April and 11 May 1993, seven male razorback suckers were collected, anesthetized with tricaine methanesulfonate (MS-222}, weighed to the nearest 10 g, measured to the nearest milli- meter (total length), and surgically implanted with a 24-month radio transmitter (-~-25 g) with an in- ternal loop antenna. Five fish were collected from a gravel bar at the Escalante spawning area (RK 500), one fish from the Yampa River spawning site (RK 555; 0.3 km upstream of the confluence with the Green River) and one fish was collected from the lower reach of Island Park (Dinosaur National Monument) in the Green River (RK 532). All fish were positively identified as males from either ex- pression of milt or heavy tuberculation of the anal and caudal fins. Fish implanted with radio trans- mitters ranged in length from 464 to 520 mm and in weight from 1,120 to 1,600 g. Transmitters were surgically implanted into the abdominal cavity, and fish were released at the capture site 10-20 min after surgery. During the spring, summer, and fall, fish were located at approximately monthly intervals from fixed-wing aircraft. In addition, weekly monitoring of fish locations was conducted by either ground- based observers (1994 only) or fixed-wing aerial surveys (1994 and 1995) from mid-April through May to determine timing of movement to spawn- ing locations. Maximum distance traveled up- stream and downstream by fish implanted with transmitters was determined fora 12-month period beginning on the date of implantation in 1993 and the second week of May in 1994. Maximum dis- tance traveled, either upstream or downstream, was computed by measuring the greatest distance traveled from the spawning site used by a given fish in the spring. Discharge and water temperature data used to compare the number of fish at spawn- ing locations were collected by the U.S. Fish and Wildlife Service (1994) and the U.S. Geological Service (1995) in Jensen, Utah (RK 505). Razorback sucker capture data consisted of elec- trofishing collection records between April and June 1975-1992. Collection effort concentrated on TABLE 1.-Maximum distance traveled upstream and downstream in the middle Green River, Utah, by adult male razorback suckers during 1993-1994 and 1994- 1995. Starting date for each 12-month period was May 14. Fish iden[ifi- 1993-1994 1994- 1995 cation number or Downstream Upstream Downstream Upstream statistic (km) (krn) (km) (lan) 177D1B 19.0 25.7 93.3 33.8 224B6B 60.4 29.8 99.0 34.6 181765 57.9 23.3 30.6 20.9 030302 21.1 0.0 4.8 45.9 180B26 40.2 0.0 30.6 1.6 180446 0.0 32.2 112.7 0.0 Mean 33.1 i8.6 61.8 22.8 SD 21.8 14.0 43.8 17.1 documented spawning (RK 492-501 and RK 555) (Tyus and Karp 1990) and pre- and postspawning staging areas (RK 480, 481, 399, and 401.5). Fish collection was associated with multiple projects, and although collection effort and area sampled were unequal through time, most effort focused near the Escalante spawning area in the spring (RK 492-501). All fish captured were marked with ei- ther dorsally attached Carlin tags (1975-1989) or internally inserted passive integrated transponder (PIT) tags (1990-1992). Data reported include those reported by Tyus and Karp (1990). Riverine Telemetry Results Among the six surviving fish (Table 1), two pat- terns of movement were observed. Four fish moved over 50 km downstream following spawn- ing at least once during the 2-year study period. Three of these four fish were located just upstream of the wetland complex on the Ouray National Wildlife Refuge. Of the six downstream movement events, all but one was initiated in either May or June. After these long downstream movements, fish moved back upstream of the Escalante spawn- ing area within 1 or 2 months. The remaining two males showed little movement and remained in the reach between Island Park and Split Mountain Canyon throughout the year. Only a single obser- vation was made during each winter. In February 1994 all six fish were located within Split Moun- tain Canyon, and in March 1995, all six fish were located within a 33-km reach of the river between Island Park (RK 534) and the Escalante spawning area (RK 501). Of interest were the two fish that returned to their original collection site in 1993 (180B26 to Yampa River and 177D1B to Escalan- t