7379 - Laserfiche WebLink

Home Browse Search

MOVEMENTS OF COLORADO SQUAWFISH 1037 ~ were tagged with a uniquely numbered Carlin dan- gler tag. These fish were obtained from a variety of sampling programs and gear. Electroshocking, seining, and trammelnetting were used in a stan- dardized sampling program, March-October 1979-1981, and electroshocking was used in April- June 1984-1988 (see Tyus 1987 for methods). Trammelnetting was conducted at areas identified by the presence of radio-tagged fish in summers 1980-1982 in an effort to find new spawning areas and to further evaluate the number offish in other areas. In 1983 and 1984, trammelnetting was con- ducted only in two spawning areas, RK 24-48 in Yampa Canyon and RK 224-256 in Gray Can- yon. Because of labor constraints, netting after 1984 was restricted to RK 25.6-30.4 in Yampa Canyon and RK 240-248 in Gray Canyon to monitor fish use of the two spawning sites. Captured fish were measured (TL, mm), weighed (g), and inspected for the presence of sex products, general condition, and any secondary sex char- acteristics (presence of breeding tubercles, color- ation, etc.). Carlin tags were attached with poly- propylene lines and tied with a surgeon's knot. Some tagged fish were retrieved with only these lines in place, and an earlier procedure for only looping the line once through the danger tag was replaced in 1986 with double loops. Colorado squawfish captured in spawning collections were also tagged. Recaptured fish bearing incision scars were anesthetized as above; old radio transmitters were removed and identified from the manufac- turer's serial number. All tag returns from these fish (N = 204), in- cluding returns from other agencies and private anglers, were used for movement information. We tagged 981 fish, and recaptured 100 of these (5 fish were recaptured two times; total recaptures = 105). Fish we tagged were also recaptured by oth- ers (N = 60 fish, 6S recaptures), and tag returns were provided by the following sources: Utah Di- vision of Wildlife Resources, 24; Colorado Divi- sion of Wildlife, 14; Bio/West, Inc., 7; Colorado State University, 4; U.S. Bureau of Reclamation, 2; private anglers, 14. Thus, there were 170 re- captures of 160 fish that we tagged. Some fish tagged by others that we subsequently recaptured (N = 29 fish, 34 recaptures) were also reported. Flow-temperature characterization. - Data on hydrological conditions were obtained from the U.S. Geological Survey, and included recordings at the Maybell and Deerlodge gauging stations on the Yampa River, Colorado, and the Jensen and Green river gauges on the Green River, Utah. . . . . These data were used in regression analyses to evaluate annual fish response to peak discharge and daily temperatures. Flow-response and temperature-response in- tervals were calculated for the initiation of Colo- rado squawfish migrations and spawning as fol- lows: for flows, I calculated an interval between the date of peak flow for each year and the average date on which radio-tagged Colorado squawfish began spawning migrations or on which they spawned (estimated from dates when migrating and ripe fish were present on spawning grounds). The lowest water temperature recorded when the earliest fish migrated and the lowest temperature recorded at the beginning of the earliest spawning period were used to evaluate fish response to tem- perature. Data from the Maybell and Jensen gaug- es were used for spawning migrations that began in the upper Yampa and Green rivers. The Deer- lodge and Green river gauges were nearer the spawning areas and were used to determine flows and temperatures during spawning. Continuous recordings of stream temperatures were not made at the Deerlodge gauge during the study period, nor at the Jensen gauge in 1987 and 1988. Stream gradients were obtained from U.S. Geo- logical Survey stream profile maps. Daily water temperatures were taken in Yampa and Gray can- yons at 0700-0800 hours and 1400-1600 hours with a hand-held thermometer during fish collec- tions. Water temperatures were not recorded ev- ery day during the spawning season, and ther- mometer records were accurate for only a low and high temperature for the spawning season. Results Migration, Movement, and Habitat Use We implanted radio transmitters in 153 Colo- rado squawfish that ranged in total length from 385 to 848 mm. Of these, 41% migrated in late spring-early summer to Gray or Yampa canyon spawning sites, 11 % were suspected migrants, and 11 % moved for unknown reasons. The remaining fish were sedentary (18%), lost (14%), or late im- plants (5%). Individuals tracked for more than 1 year (N = II) included eight tracked in 2 consec- utive years and three tracked for 3 years. Of these, five were classified as nonmigratory one year and migratory the next year, and five were migrants one year and lost the next. After the summer spawning season, migrants usually returned to ar- eas they had occupied in the spring. Colorado squawfish were radio-tracked in a va-