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Fishery Bulletin 93(1). 1995 



from 24 to 114 d (Bumguardner et al., 1992). A simi- 

 lar wire tag loss rate was observed in striped bass 

 tagged horizontally in the cheek muscle (22.2-30.7% 

 retention over the first 70 d; Dunning et al., 1990). 

 However, Dunning et al., (1990) also reported that 

 wire retention rates substantially increased when 

 stripped bass were tagged in the snout (63-98.5%), 

 nape (93.8-99.3%), or vertically in the cheek (82.7- 

 87.0%) over the first 70 days. Also, Klar and Parker 

 (1986) showed 99% tag retention after 90 days if wires 

 were injected into the epaxial muscle of striped bass. 

 Our results agree with the higher tag retention rates 

 reported by Dunning et al., (1990) and Klar and 

 Parker (1986); there was little indication of tag loss 

 in the first days after marking. We suggest that 

 higher wire retention resulted from mark location, 

 because current wires were injected deep (4—5 mm) into 

 the epaxial muscle and had little chance of expulsion. 



Although wire tags showed the best overall per- 

 formance compared with other tags, the method was 

 the most labor intensive of all methods, because of 

 the required dissection, removal, and reading of 

 wires. If individual growth rates are needed and both 

 personnel and budget are limiting, plastic tags may 

 be useful. Plastic tags can be read directly without 

 harm to the fish, but they also showed significant 

 tag loss compared with other methods and should be 

 limited to short experiments of no more than 25 days. 



Paint marking methods showed greater mortali- 

 ties and lower retention times compared with other 

 methods but are useful in situations where fish can 

 only be held for short periods (1-2 h, see Weinstien 

 et al., 1984). However, paint marking methods should 

 also be limited to short-term experiments because of 

 significant mark loss after 25 days. 



If fish movements or survival are the objectives 

 and fish can be held for long (=15 h) marking peri- 

 ods, then OTC or alizarin may be the best marking 

 methods. Both methods showed higher tag retention 

 ( 100%) and lower mortality rates compared with plas- 

 tic minitags or paint methods. Other studies have 

 shown long-term retention for these chemicals: for 

 example, OTC marks in chum salmon, Oncorhynchus 

 keta (Bilton, 1986) and alizarin marks in P. major 

 (Tsukamoto et al., 1989) were both detected two years 

 after marking. Another advantage of OTC and al- 

 izarin staining was that handling was minimal and 

 probably caused the least amount of stress among 

 all the marking methods, as reflected in the lower 

 mortality rates. Therefore, these fluorescent stains 

 would be most suitable for long-term studies where 

 individual growth rates are not needed and for batch 

 marking large numbers of fish, for example prior to 

 release of hatchery reared fish (Tsukamoto et al., 

 1989;Secoretal., 1991a). 



One difference in the present study was the use of 

 oxytetracycline-dihydrate instead of oxytetracycline- 

 hydrochloric acid (HCL), as used in other studies. 

 (Hettler, 1984; Tsukamoto and Shima, 1990; Secor 

 et al., 1991a). The dihydrate form of OTC was ad- 

 vantageous in that it did not cause a reduction in pH 

 as observed with the HCL form. This difference may 

 account for the low mortality observed after 15 hours 

 in the OTC bath (i.e. no fish died during the 15-h mark- 

 ing period). One advantage of the alizarin stain over 

 the OTC marker was the ease in detecting the fluores- 

 cent marks. When whole otoliths were examined only 

 2 of 91 alizarin otoliths needed further cutting and pol- 

 ishing to detect the stain, whereas 23 of 83 OTC otoliths 

 needed sectioning before OTC marks were visible. 



As indicated by growth rates, fish acclimated well 

 to the closed seawater system. Although we did not 

 have a control group of fish, growth rates in the 

 present study (1.0-1.1 mm SL/d) were similar to or 

 greater than previous studies of unmarked S. 

 ocellatus of similar sizes and temperatures as the 

 current study: 0.8 mm/d from Tampa Bay (Peters and 

 McMichael, 1987), 0.8 mm/d from Charleston Har- 

 bor (Daniel, 1988), and 1.0 mm/d for reared fish in 

 Texas (Colura et al., 1990). Also, we were not attempt- 

 ing to compare growth rates of marked fish with those 

 of wild populations or those of unmarked laboratory 

 fish but rather to determine the most useful tag of 

 the methods tested. 



Thus, we recommend wire tags when individual 

 marks are needed because of lower mortality and 

 higher mark retention compared with those from 

 plastic minitags. We recommend alizarin when batch- 

 marking methods are needed and individual growth 

 rates are not critical, because of lower mortality and 

 higher retention compared with those from paint 

 methods and because of ease of detecting mark com- 

 pared with OTC marking. 



Acknowledgments 



We thank J. Lindstrom and J. Mang for help in rear- 

 ing and sampling S. ocellatus. We thank L. Collins 

 for review of an early draft. This research was funded 

 through a Saltonstall-Kennedy grant USDC- 

 NA27FD0063-01, National Marine Fisheries Service, 

 National Oceanic and Atmospheric Administration. 



Literature cited 



Bilton, H. T. 



1986. Marking chum salmon fry vertebrae with oxytetra- 

 cycline. N. Am. J. Fish. Manage. 6:126-128. 



