7379 - Laserfiche WebLink

Home Browse Search

1036 pulsed DC unit in April and May; however, a few fish (N = 7) were taken later in the year in trammel nets. We anesthetized the fish with tricaine (MS-222, 200 mgIL), inserted beeswax-coated transmitters into the body cavity via lateral incision, and closed the wound with 2.0-mm nylon sutures of triple- tied, individual surgical knots (Tyus and McAda 1984; Tyus 1988b). Four types of transmitters, which ranged in weight from 11 to 23 g in air, were used. All transmitters emitted unique signals (frequency and pulse rate) in the 40.66~0. 700- MHz frequency range. Theoretical transmitter life (Tyus 1988a) ranged from 150 to 550 d. Radio receivers were Smith-Root RF-40 and SR-40 types. Radio-tracking was conducted from boat and airplane by use of omnidirectional whip and bidirectional loop antennas. Eleven fish were tracked for more than I year (five fish were tracked 455-542 d; transmitters were reimplanted in six other fish). This permitted a comparison of be- havior in different years. Radio-tracking detected fish that we and other investigators had radio-tagged. Of 153 radio- tracked fish (including 11 fish tracked for more than 1 year), 119 were radio-tagged by me or an assistant, and 34 were radio-tagged by others: 4 by the Utah Division of Wildlife (S. R. Cranney, personal communication); 6 by the Colorado Di- vision of Wildlife (P. C. Martinez, personal com- munication); 12 by Colorado State University (E. J. Wick, personal communication); and 12 by Bioi West, Incorporated (R. A. Valdez, personal com- munication). Capture locations of radio-tagged Colorado squawfish included the Yampa (N = 32), Green (N = 101), White (N = 19), and Duchesne rivers (N = 1). Fish were tracked in the lower 552 km of the Green River, lower 192 km of the Yampa River, lower 200 km of the White River, and lower few kilometers of the Duchesne River and other smaller tributaries (Figure 1). The location of each radio-tagged fish was fixed by triangulation (Bovee 1986; Tyus 1988a). Locations were recorded in river kilometers (RK) upstream from the mouth of each river, and general habitat type and sub- strate (direct observation and feel) were recorded at the apparent signal source (Priede 1980). Mi- crohabitat data, including water depth (direct measurement with a rod) and water velocity (Marsh-McBimey current meter at 0.6 of the depth below the water surface) were recorded during the spawning season for fish that remained in one lo- cation for 30 min or longer. Ifa located fish could ....... ~~ TYUS FIGURE I.-Green and Yampa rivers, where move- ments and migrations of Colorado squawfish were stud- ied, 1980-1988. not be disturbed by wading or probing after the 30-min period, triangulation was repeated. If, af- ter a second attempt, fish movement could not be obtained, the record was not used. Data collected from airplane flights were not used to determine habitat. Radio-tagged fish were classified according to their movements during an approximate spawn- ing season (June 15-August 1) as follows: mi- grants-fish moving to one of two known spawn- ing areas during the spawning period; suspected migrants-individuals moving to an area consid- ered suitable for reproduction during the spawn- ing period (similar substrate and habitat to known spawning areas); unknown-fish moving 30 km or more to areas in which no spawning area was suspected; sedentary-fish exhibiting only local movements (<30 km) in which no migratory pat- tern was evident; lost-fish whose signal was lost after a month or less of tracking, or fish with which no contact was made for a month or more during the spawning season; and late implants-fish ra- dio-tagged during or after the spawning season. Tagging and recapture. -Colorado squawfish longer than 350 mm total length (TL) captured in the Green River basin by USFWS in 1979-1988 r, . "" '1 ..