NOTE Winner et al : Evaluation of T-anchor and dart tags for use in marking Saaenops ocellatus 



731 



ated with tagging was monitored for the first 111 days 

 of the experiment. 



T-anchor tags (lEX tags"^, Fig. 1) had an 18-mm 

 "T" with molded polyethylene on both sides for sup- 

 port. Attached to the "T" portion of the tag was a 42- 

 mm streamer, the distal two-thirds of which was en- 

 cased in polyethylene. T-anchors were inserted 

 through a 1-mm-diameter hole made with a pointed, 

 stainless-steel rod. Tags were inserted on the left 

 ventral side of the fish near the distal end of the pel- 

 vic fin. Once inserted, the tag streamer was pulled 

 so that the T-anchor rested along the body cavity wall, 

 with the streamer protruding. 



Dart tags (PDX tags-, Fig. 1) had a 9-mm, semi- 

 rigid plastic barb attached to a 45-mm plastic 

 streamer that was encased in polyethylene. Dart tags 

 were inserted into the pterj'giophores of the spinous 

 dorsal fin by using a stainless-steel canula. 



We dipped all tags and applicators in Betadyne 

 before tagging each fish to minimize the possibility 

 of infection. The streamer of each tag was imprinted 

 with a unique tag number so that we could identify 

 individual specimens. 



All red drum used in this experiment were spawned 

 and maintained in ponds at the Florida Department 

 of Environmental Protection's Stock Enhancement 

 Research Facihty (SERF) in Port Manatee, Florida. 

 The holding ponds were drained at 290 days after 

 spawning and fish were dip-netted to a small hold- 

 ing tank, where they were anesthetized (Tricaine 

 menthanesulphonate, MS222, 100 ppm). Fish were 

 measured (SL mm) and randomly assigned to one of 

 three treatment groups: dart tagged, T-anchor 

 tagged, and controls (handled but not tagged). Each 

 treatment group contained 100 fish (mean SL=140 

 mm, mean weight=40 g), divided equally between two 

 1.5-m-diameter net pens with a volume of 2.12 m'^ 

 Net pens were constructed of 6.25-mm knotless ny- 

 lon mesh and were submerged within a closed 

 aquarium system (>79,000 liters) with supporting 

 aeration, bio-filter, and rapid sand filter. Salinity ( '?<:), 

 dissolved oxygen (mg/L), and temperature (°C) were 

 monitored daily. Ammonia concentration (NH.^^, 

 mg/L) was monitored periodically. Fish were fed a 

 combination of cut squid and commercially prepared 

 pelletized fish food at a rate of 2-5'7f of body weight 

 per day. 



Net pens were checked daily for fish mortalities 

 and shed tags. Standard length (SL mm), date, tag 

 type, tag number, and pen number were recorded for 

 all fish mortalities. At 66, 111, and 423 days after 



\ 



B 



Figure 1 



External tags used to mark 

 hatchery-reared red drum; 

 I A) T-anchor (lEX tags) and 

 (B) dart (PDX tags). Both 

 tags are manufactured by 

 Hallprint Ltd., Holden Hill, 

 Australia. Shown at 75'7< of 

 actual size. 



' Hallprint Ltd., 27 Jacobsen Crescent, Holden Hill, South Aus- 

 tralia 5088, Australia. 



tagging (DAT), fish from all net pens were measured 

 (SL mm), tag numbers checked, and tag wounds ob- 

 served for degree of healing (wound open or closed). 

 Control fish were removed from the study at 1 1 1 DAT. 

 We continued to monitor tagged fish from 111 to 423 

 DAT so that we could evaluate long-term tag reten- 

 tion. All fish were treated ior Amyloodinium sp. and 

 parasitic copepods at 21 DAT. 



Standard length measurements of red drum were 

 compared between net pens at 0, 66, and 111 DAT by 

 using a nonparametric Kruskal-Wallis one-way 

 ANOVA on ranks test (a=0.05). Instantaneous sur- 

 vival rates of red drum were compared between treat- 

 ments by using a two-way (% offish alive) repeated 

 measures ANOVA (a=0.05) on arcsine-transformed 

 data. Net pen was used as the subject, with tag type 

 as a group factor and days as a level factor (Fox et 

 al., 1995). 



Results and discussion 



Tag-retention rates in red drum in this study were 

 similar for both T-anchor and dart-tagged fish (Table 

 1 ). Average retention rates for T-anchor and dart tags 

 were, respectively, 98^7^ and 99'A at 66 DAT; 97% and 

 95% at 111 DAT; 91% and 89% at 423 DAT. No tags 

 were shed until 41 DAT, and nearly all shedding 

 stopped by 150 DAT (Fig. 2). Both tag types were 

 retained in some red drum as large as 485 mm SL. 

 Wallin et al. ( 1997) also reported high short-term (30 

 days) retention rates (100%) of T-anchor tags in ju- 



