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. ~ ' '~ MANAGEMENT BRIEFS 259 much lower than the 59% reported by Chisholm and Hubert (1985), and it was lower than the rates of 71 % and 53% reported for channel catfish /c- ta/urus punctatus by Summerfelt and Mosier (1984) and Marty and Summerfelt (1986). Rainbow trout held at Jones Hole showed ob- vious effects of containmen't in concrete raceways. Loss of the ends of the fin rays, damaged and reduced fins (particularly the caudal and pelvic fins), and inflamed incisions were observed. These fish obviously were in poorer condition than those held in the smoother, round tanks at Logan, and this may have contributed to an apparently greater expulsion rate (for beeswax and paraffin coatings: 10% at Jones Hole versus 4% at Logan). We note that about 27% of the 30 trout implanted by Chis- holm and Hubert (1985) died, which suggests that many of their fish were in poor condition. This may have exacerbated the expulsion rate in their study. Condition of DTRs inside the body cavity at necropsy ranged from resting or encapsulated against the body wall to free-floating without tissue encapsulation. Some DTRs were anterior to the incision and still in the location of initial place- ment, but most were lateral or posterior to the incision. Beeswax-coated DTRs were rated as moderately or heavily encapsulated, whereas par- affin- and silicone-coated transmitters were slight- ly encapsulated or free in the body cavity. Thus, it is possible that the heavier tissue encapsulation noted for the beeswax coatings aided retention of the DTRs, as suggested for other species by Tyus (1988). The low expulsion rate ofDTRs obtained in this study, combined with results of field studies with similar techniques (Tyus 1988), indicated that long- term (over I year) retention of most transmitters is possible. Beeswax-coated transmitters were rarely expelled, and we recommend the use of beeswax pending the development ofa better coat- ing. AcknoK'/edgments. - This project was supported in part by the Utah Division of Wildlife Resources, the U.S. Bureau of Rec1amation, and the U.S. Fish and Wildlife Services. Utah State University and Jones Hole National Fish Hatchery provided space and fish care. K. M. Paulin, L. A. Trinca, and S. Poulson assisted with fish implantation and nec- ropsy. Dow Coming Corp. provided Silastic@. C. A. Karp and T. E. Wissing improved an earlier draft manuscript. References Chisholm, I. M., and W. A. Hubert. 1985. Expulsion of dummy transmitters by rainbow trout. Trans- actions of the American Fisheries Society 114:766- 767. Marty, G. D.. and R. C Summerfelt. 1986. Pathways and mechanisms for expulsion of surgically implant- ed dummy transmitters from channel catfish. Trans- actions ofthc American Fisheries Socicty 115:577- 589. Summerfelt. R. C, and D. Mosier. 1984. Transintes- tinal expulsion of surgically implanted dummy transmitters by channel catfish. Transactions of the American Fisherics Society 113:760-766. Tyus, H. M. 1988. Long-term rctention of implanted transmitters in Colorado squawfish and razorback sucker. North American 10urnal of Fishcries Man- agement 8:264-267.