7985 - Laserfiche WebLink

Home Browse Search

D"cember 1993 Trammdl "t al.-Colorado squawfish 363 . ~ <.' ." .tf~":. .~~~~~:: :.....;\>~~ l;:"::';';-::;' ;7':.:.:- " veys by cnow of the reservoir and river indi- cated the stocked Colorado squawfish had dis- persed throughout the reservoir and moved downstream. The study reported here was begun in 1989 to further evaluate dispersal of the 1988 stock and to assess the results of subsequent stock- ings of Colorado squaw fish in Kenney Reservoir. Our primary objectives were to evaluate Colorado squawfish ecology and behavior as they related to attempts to artificially establish these fish in the reservoir as a sport fish, and to evaluate the potential of a sport fishery based on stocked squawfish. MATERIALS AND METHODS-The study area en- compassed the White River from 16 km above Kenney Reservoir at river-kilometer (RK) 192.7 downstream to the Colorado-Utah border (RK 115.5; Fig. 1). In 1988 and June 1989, the river was sampled 16 km upstream and downstream from the reservoir. As it became apparent the squawfish were moving down- stream, the study area below the dam was extended to the Colorado-Utah border in July 1989. The river was subdivided into five sections as indicated in Fig. 1. Kenney Reservoir's upper limit was designated as RK 175.9 and the lower limit as RK 167.8 at the dam axis. The reservoir is 8 km long and 1.2 km across at its widest point, with a maximum depth of 15.2 m near the dam. When filled in 1985 it covered 275 ha and held 17 million m' of water. The high silt load of the White River decreased the reservoir's capacity an un- determined amount by filling the upper end of the reservoir with silt deposits for about 1.5 km. There is an outlet gate at the base of the dam but most of the flow was released over the spillway during the study to allow repair and modification of the outlet gate. Dexter National Fish Hatchery and Technology Center (DNFHTC) staff in New Mexico provided Colorado squawfish eggs to Willow Beach National Fish Hatchery, Arizona, where they were raised for the stocking program. The initial goal of stocking 150,000 Colorado squawfish during the three-year study was not met due to mortality during rearing. Only 96,597 age-1 fingerlings were stocked into Kenney Res- ervoir and all received an internal tetracycline mark along with an external identification mark for each batch stocked (Table 1). Kenney Reservoir was sampled by seining, gillnet- ting, and e1ecrrofishing (Table 2). The bag seine used was 12.2 m long, with 9.5 mm mesh. Shoreline areas were seined monthly from May through November. Catch per unit of seining effort was derived by dividing the total number of fish caught by the units of seining effort expended during the month. One unit of effort was equal to the seining of 100 m2. Two multifilament gill nets were used; one was 45.7 m long and 3.6 m wide with 19-mm mesh and the other was 30.5 m long and 1.5 m wide with 19-mm mesh. From May through October, gill nets were set overnight in all maj~r hab- itats (e.g., shallow coves, deep coves, cliffs, slopmg ar- eas, surface, bottom, midlake). Electrofishing was con- ducted with a boat-mounted variable voltage pulsator (Coffelt Mfg. VVP-15), using spherical electrodes. Six to seven IS-minute reaches of shoreline were sampled May through August in 1989, and in July 1990.. The White River was sampled similarly with semes, gill nets, e1ectrofishing and drift nets (Table 2). Back- water sites were seined monthly from June through September, with effort and location varying each.month because of changes in flow. Gill nets were occaSIOnally set im~ediately below the dam to take advantage of the reduced current while the bottom outlet of the dam was closed. Electrofishing was conducted once each May, as low flows precluded e1ectrofishing in later months. The drift nets were; two rectangular frame 2.4 m x 0.6 m, 6.3 mm mesh nets, and two 1.2 m diameter shad trawls. Drift nets were set in the chan- nels directly below the spillway and were checked twice daily; these nets consisted of two rectangular-frame nets with 6.3-mm mesh and two shad trawls 1.2 m in di- ameter. Telemetry observations of adult Colorado squawfish of both hatchery and wild origin were made in 1990. Seven squaw fish were surgically implanted with both radio and sonic transmitters on May 12, 1990. Use of the two types of tags in each fish facilitated tracking in both the reservoir and river. Four fish were taken from broodstock at DNFHTC, and three wild fish were collected from the White River for implantation. Surgical procedures followed those of Tyus and McAda (1984). The combined weight of the tags ranged from 1.7 to 3.5% of the weight of the fish. All fish received a PIT (Passive Integrated Transponder) tag (Chart and Bergersen, 1988). Radio transmitters were Advanced Telemetry Sys- tems (A TS) modules with loop antennae, powered by 6-month mercury batteries, and operating in the 40.320 to 40.680 MHz range. These tags were monitored with an ATS programmable digital radio search receiver, using a whip antenna and a directional loop antenna. The sonic transmitters, 14-month Sonotronics, Inc., tags, were monitored with a Sonotronics Model DH-2 hydrophone and USR-SB digital receiver system. Monitoring of telemetered fish was conducted bi-week- Iy in the reservoir and monthly in the river. .~I.JlilRtU(ll~ RESULTs-When released into the reservoir, fingerling Colorado squawfish swam away in compact schools and quickly dispersed through- out the reservoir. Specimens were collected across the reservoir from the stocking site near the spill- way in three days, and were found at many sites throughout the reservoir within one week. Sites where the stocked fish were collected remained well distributed along the shoreline. .:~~~p~:~'~~: ~~~:,. ~..: ~ ~