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Ir~ .\A.5 - ~ l q~ 1" [ North American Journal of Fisheries Management 8:264-267, 1988 OYf74- Long-Term Retention of Implanted Transmitters in Colorado Squawfish and Razorback Sucker HAROLD M. Tyus u.s. Fish and Wildlife Service, 1680 West Highway 40, Room 1210 Vernal, Utah 84078, USA Abstract.-Retention time and effects of surgically implanted radiotransmitters on growth and survival were evaluated for Colorado squawfish Ptychocheilus lucius and razorback sucker Xy- rauchen texanus from the Green River, Utah. No transmitter expulsion was detected during radiotracking of 97 Colorado squawfish and 9 razorback suckers that had been implanted between 1978 and 1985. Of 14 transmitters removed from recaptured fish, 12 had been retained from 3 months to 8 years in Colorado squawfish and 2 had been retained for I year in razorback suckers. This suggests surgical implants may be retained for the life of the fish. Growth rates of implanted fish did not differ from those of non implanted fish ofthe same size range. There was no difference in mortality between implanted and dangler-tagged fish. Beeswax provided a suitable coating for the surgical implants. I Radiotelemetry is a relatively new and rapidly developing methodology for monitoring fish be- havior in natural environments. Its use is partic- ularly recommended in riverine and other systems where visual observations are precluded by tur- bidity and other types of biotelemetry have proven unsuitable (Stasko and Pincock 1977; Winter 1983). Radiotransmitters were designed for un- derwater application in the 1960s, and many fish species were monitored with externally and inter- nally attached radios during the 1970s (reviewed by Tyus 1982; Winter 1983). Although various attachment methods and results of their use have received attention (Stasko and Pincock 1977; Mi- nor 1981; Ross and McCormick 1981; Winter 1983; Mellas and Haynes 1985), few studies have addressed the effects of surgically implanted trans- mitters on growth and survival offishes in natural environments. This paper evaluates long-term re- tention of implanted transmitters by, and their effects on the growth and survival of, Colorado squawfish Ptychocheilus lucius ilnd razorback sucker Xyrauchen texanus in the Green River, Utah. Colorado squawfish is listed as endangered by the U.S. Fish and Wildlife Service (USFWS 1974) and razorback sucker is a candidate for list- ing (USFWS 1985). Methods Ninety-seven Colorado squawfish and nine ra- zorback suckers were surgically implanted with radiotransmitters from 1978 to 1985 (Holden and Selby 1978; Tyus and McAda 1984; Tyus et al. 1987). Radiotransmittershadcasingsofthreetypes: polystyrene, polycarbamate, and acrylic resin. All except the polystyrene capsule had been coated 264 with beeswax prior to implantation, as recom- mended by the AVM Instrument Company, Limitedl (B. Kermeen, Livermore, California, personal communication). Transmitters were im- planted through a lateral incision (Tyus and McAda 1984). Ten Colorado squawfish (12 implantations) and two razorback suckers (2 implantations) were re- captured and their transmitters were recovered (Tyus et al. 1987). These fish were recaptured by a variety of methods including electrofishing, net- ting, and angling. Two Colorado squawfish were necropsied in 1980 (Tyus and McAda 1984) and their transmitters were removed after the fish had retained them 3-5 months. Of the 14 recovered transmitters, 11 were implanted and retrieved by me, I was implanted by me and retrieved by another, and 2 were implanted by others and re- trieved by me. One Colorado squawfish was im- planted in 1978 by P. B. Holden (Bio/West In- corporated, personal communication), and again in 1985 by me. The transmitter in another Colo- rado squawfish was replaced after I year. Recaptured fish bearing incision scars or exter- nal dangler-tags (evidence of previous implanta- tion) were anesthetized and incised either directly over detected transmitters or near old scars to maximize the probability of transmitter retrieval. Following transmitter removal, incisions were closed with individual sutures and the fish were released. Growth and recapture rates of implanted Col- 1 Reference to trade names does not imply U.S. Gov- ernment endorsement of commercial products.