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.290 ,il . J The Southwestern Naturalist vol. 29, no. 3 August 1984 Tyus and McAda-Squawfish Movements 291 ~ ! N I / ----1 UTAH COLORADO and have a life of about 6 months. All units transmined in the 40.660-40.700 MHz frequency range. Each transminer had a unique signal (frequency vs pulse rate) so that individual fish could be identified. Radio receiver sets used were Smith-Root RF-40 and SR-40 models. The RF type enabled the investigator to identify any particular frequency transmined at 40 MHz. The SR receiver was a "search" type and received all emined frequencies in the frequency range. Omni-directional and pin-pointing type (bidirectional) antennas were employed. A Larson- Kulrod whip antenna was used to search for implanted fish. This antenna was mounted on a 20 cm square steel plate elevated about 4 m above the water when mounted on a boat, or mounted directly to an airplane, or helicopter strut. A Smith-Root loop antenna (directional) was used only to triangulate fish location, from boat or shore. It was necessary to use aircraft to keep contact with several fish at one time. The most slu:cessful aircrah used was a helicopter. since airplanes cannot rly safely in most canyon areas. The radiotelemetry program utilized two different methods for recording information about habitat preferences and movement. Long distance movement was determined by anempting to locate all radiotagged fish on a 1-2 day interval. The location of a fish was recorded as a single contact when encountered. In order to obtain specific information on movement and habitat preferences, a die I sampling procedure was employed. Observations were made continuously over a 24 hour basis as follows: I. Fish to be studied were selected by tag number from a table of random digits. 2. Twenty-four hour day was divided into three eight-hour periods and one period selected at random. A fish was then monitored during this period. If a fish remained stationary for 30 minutes, then its location was recorded every 15 minutes, along with the water depth and velocity, substrate type and habitat type. 3. After a fish had been monitored [or three eight-hour periods, the [ish with the next consecutive tag number was then selected [or study. The location of each radiotelemetered' fish was carefully fixed and recorded relative to the distance upstream [rom the mouth o[ each river (river mouth = 0 km). If the fish remained in one location for 30 minutes it was assumed this habitat was preferred and microhabitat information was recorded, including the general habitat, substrate type, water depth and water velocity. Water depth, velocity and substrate measurements were taken only when the [ish moved to another location or at the end of the study period. These precautions were taken in order to minimize disturbance to the fish. Water depth was recorded by direct mesurement with a wading rod and water velocity was measured 0.6 o[ the distance from the water surface with a Marsh- McBirney. current meter. Substrate type was obtained by direct observation and by feel. The MANAGE data based management system developed by the FWS Western Energy and Land Use Team (WELUT) in Fort Collins, Colorado was used [or storage, retrieval and manipulation of the data (Shumate, et aI., 1981). WYOMING o , SCALE IN KILOMETERS 50 100 150 200 2~0 50 100 150 SCALE tN MILES o ARIZONA t ------- ------ , , I , i NEW MEXICO RESULTs.-Movement.- Three types of behavior were exhibited by the 31 radio-implanted fish. One fish was used as a test animal early in 1980, It was in poor condition when released and only monitored four days until its recapture, after which it died. Its steady downstream movement was indicative of its poor health and similar to the behavior of another Colorado squawfish that moved downstream and was later found to be dead. Of the remaining 29 Colorado squawfish only 15 were monitored for .') months or more. These 15 fish exhibited two movement patterns: highly mobile and sedentary. The total distance moved by 9 mobile fish averaged 338 km (Table I) and most of the movement occurred in mid-June through July. Contact was lost with three of the six sedentary.fish for a month of more during this time period and, since those fish could also have been active during that period they were not classified as to movement pattern. The remaining three fish were classified as sedentary and their total movement averaged only 42 km (Table I) during the study period. One Colorado squawfish from the sedentary group and one from the mobile group were recaptured and dissected. The fish from the sedentary group was a very immature male but the mobile fish was a female in an FIG. I.-The Green River Basin. After their capture, the Colorado squawfish were placed into a 200 mg/L solution of tricaine methylsuHonate. When the fish were anesthesized, they were surgically implanted with radiotransminer modules using a procedure similar to that of Bidgood (1980). Sutures were individual (usually five) rather than the continuous suture used by Bidgood, and the incision was made laterally, immediately anterior and slightly dorsal to the insertion of the right pelvic fin. Implanted fish were held five days in 1980 in order to determine the results of the surgery. In 1981 the fish were released after implanting them in order to reduce stress (Hart and Summerfelt, 1975) associated with holding them. Surgical implantation was completed with A VMo company and Smith-Root Company fish transminer modules dipped in melted beeswax. These modules weighed approximately 10 to 20 g respectively in air and about 3.5 to 6 g in water. The units are powered by mercury banerie,