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Fishery Bulletin 97(3), 1999 



venile Centropomus undecimalis. Collins et al. ( 1994) 

 found that T-anchor tags had higher long-term re- 

 tention rates than did dart tags in juvenile Ac/penser 

 brevirostrum (T-anchor: 92% at 306 DAT; Dart: 509^ 

 at 154 DAT). The low retention rates of dart tags in 

 their study may be explained by the fact that the 

 posterior position of the dorsal fin in these fish sub- 

 jected the tags to the constant motion of the caudal 

 fin and thus enlarged the wound around the tag in- 

 sertion point (Collins et al., 1994). 



Compared with other external tags, T-anchor and 

 dart tags appear to have superior retention rates in 

 small red drum (<380 mm SL). Floy dorsal, Monel 

 metal operculum, Monel metal jaw, Petersen oper- 

 culum, Petersen dorsal, streamer dorsal, and Carlin 

 dangler tags all yielded lower retention rates (<50% 

 after 154 DAT, Hein and Shepard, 1980a) than did 

 the T-anchor and dart tags tested in this study. 



At 66 and 111 DAT, none of the T-anchor tag 

 wounds had healed. Other studies have also shown 

 that tag rotation and movement irritated the inci- 

 sion site, inhibited healing, and left an opening into 

 the body cavity (Smith et al., 1990; Collins et al., 

 1994). Wallin et al. ( 1997) suggested that long-term 

 retention of T-anchor tags may be reduced because 

 of the open tag wounds; this was not observed in the 

 423 days of our study. The anchor portion of some of 

 the T-anchor tags protruded through a hole in the 

 abdominal wall that was separate from the tag in- 

 sertion point. This may have been an early stage of 

 tag shedding, although it was never verified that the 

 protruding tags were actually shed. Similar results 



have also been reported in studies with disk-type 

 internal-anchor tags (Vogelbein and Overstreet, 

 1987; Mattson et al., 1990). 



All dart-tag wounds appeared to be healed by 66 

 DAT. Increases in fish body size during the course of 

 the study caused the streamer portion of some dart 

 tags to become engulfed by the body-wall tissue. This 

 made the tags difficult to detect and impossible to 

 read without dissection. A longer tag streamer could 

 minimize this effect, but it could increase stress on 

 smaller fish during tagging. Simmons and Breuer 

 (1982) also reported tissue growth over tags, which 

 reduced the ability to identify tagged red drum. 



Tagging did not appear to adversely affect red drum 

 survival. There was no significant difference in in- 

 stantaneous survival estimates between treatments 

 (F=2.2, P=0.26). Mean percent survival of control, T- 

 anchor, and dart-tagged fish was, respectively, 79%, 

 68%, and 79% at 66 DAT and was 67%, 65%, and 

 77% at 111 DAT (Table 1). Nearly all mortality oc- 

 curred during the first 40 days of the experiment; 

 67% of all T-anchor and 83% of all dart-tag mortali- 

 ties occurred during this time period (Fig. 3). These 

 results are consistent with those of other studies in 

 which these tag types were used (Collins et al., 1994; 

 Szedlmayer and Howe, 1995; Wallin et al., 1997). 



Initial lengths of red drum were not significantly 

 different between treatments (//=3.1, P=0.68, df=5. 

 Table 1 ). Red drum lengths at 66 and 1 1 1 DAT were 

 also not significantly different between treatments 

 (66 DAT: //=3.9, P=0.56, df=5; HI DAT: H=6A, 

 P-Q.21, df=5), suggesting that tagging did not ad- 



