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~ .. J YUSp ~_. bVvft\'iCK> /vtcj~'ci~ ~o7 g / jY~4 '~: ':"-~~~'~^:_:~~:~:':')"~'~~~:'_~; <..:r.: <~!d North American Journal oj Fisheries Management 4: 177-180, 1984 o I .50'b . ~ Use of Radiotelemetry for Obtaining Habitat Preference Data on Colorado Squawfish ) HAROLD M. Tyus, BOB D. BURDICK, AND C. W. McADA u.s. Fish and Wildlife Service 447 East Main Street Vernal, Utah 84078 ABSTRACT Habitat preferences of Colorado squawfish Ptychocheilus Lucius were obtained from 2,329 ob- servations of 22 radiotelemetered fish and compared with habitat information obtained at the point of capture for 241 fish. Depth, velocity, and substrate preferences also were compared by these two methods. Radiotelemetry observations appear to avoid some of the bias from conventional collec- tions, and can provide a better understanding of habitat requirements for stream fishes. Stream fishes are difficult to study (Hynes 1970) and behavioral information in turbid rivers must be obtained by capturing fish in situ because vi- sual observations are impossible. Habitat pref- erence data for endemic Colorado River fishes (Tyus et al. 1982) have been obtained by re- cording habitat information at the point of cap- ture of individual fish. These data are biased by differences in collection techniques and the type of gear employed. Radiotelemetry has been used primarily to obtain information about general fish movement but is seldom used for micro- habitat studies. However, fish radiotelemetry of- fers great promise for such studies (Stasko and Pincock 1977) and the use of internal vs. external transmitters (Chamberlain 1979) avoids the ab- normal behavior observed in some telemetered fishes (Ross and McCormick 1981). In this pa- per, we discuss habitat preferences for Colorado squawfish (Ptychocheilus lucius) using data ob- tained by radiotelemetry and that obtained from conventional fish collections as two methods for obtaining habitat preference information. We hope that fish managers will explore the use of radiotelemetry as a method for learning more about the behavior and habitat preferences of stream fishes, especially in turbid streams where visual observation is precluded. ] METHODS ItadioteleD1etry Colorado squawfish were collected by electro- fishing in April and May. Although fish were more difficult to collect in cold water, better post- operative recovery was anticipated. The fish were obtained from the Green River in 1980 and the Green, White, and Yampa rivers in 1981 (Fig. 1). After their capture, the fish were anesthetized with a 200 mg/liter solution oftricaine methane- sulfonate. Surgery was conducted immediately thereafter using a procedure similar to Bidgood (1980). The incision was made on the lateral side of the fish, immediately anterior and slightly dor- sal to the insertion ofthe right pelvic fin. Surgical implantation of Sm-l (A VM Company) fish modules was made by inserting the beeswax- dipped module into the peritoneum. The inci- sion was closed with individual sutures (usually five), and the fish were held in river holding pens 3-5 days before release at point of capture. No ill effects from the surgery were noted. The Sm-l radiotransmitter modules weighed only II g and were powered with a mercury bat- tery having a theoretical life of about 200 days. Smith-Root Model RF-40 and SR-40 radio re- ceivers were used to monitor the 40.660-40.700 Khz transmissions. Fish location was fixed with a small bi-directional loop antenna after their location was approximated with a more sensitive omnidirectional whip antenna. The accuracy of the locating method (triangulation) was un- known, but repeated triangulations indicated the method was precise. Antennas were used from boats and shore to obtain fish position. Habitat preference information was obtained from monitoring the location of Colorado squawfish in the field and measuring habitat pa- rameters at located sites. The initial contact site was recorded and diel studies. were made using the following sampling design: Fish were selected by tag number using a table of random digits. The day was divided into three 8-hour periods 177