An evaluation of six marking 

 methods for age-0 red drum, 

 Sciaenops ocellatus* 



Stephen T. Szedlmayer 

 Jeffrey C. Howe 



Department of Fisheries and Allied Aquacultures 

 Auburn University Marine Extension and Research Center 

 41 70 Commanders Drive, Mobile. Alabama 3661 5 



Mark-recapture studies of fishes can 

 reveal valuable information on move- 

 ment, mortality, and growth rate 

 (Parker et al., 1990). Despite the 

 many successful methods that have 

 been developed for adult fish, mark- 

 ing of small juvenile fishes is prob- 

 lematic (Chapman and Bevan, 1990). 

 Age-0 fish are typically too small and 

 delicate for many marking methods. 



A few methods for marking age- 

 fishes have been developed: coded 

 wire microtags (Thrower and 

 Smoker, 1984; Brodziak et al., 1992; 

 Bumguardner et al., 1992); spray 

 paint marking (Phinney et al., 

 1967; Pierson and Bayne, 1983); 

 fluorescent staining (Hettler, 1984; 

 Secor et al., 1991a; Szedlmayer and 

 Able, 1992); and external plastic 

 minitags (Floy Tag and Mfg. Co., 

 Inc., Seattle, WA). All of these 

 methods have advantages and dis- 

 advantages based on the attributes 

 of each species. Thus, there is a 

 need to test different marking 

 methods on small size classes of 

 different species to determine the 

 most suitable methods. 



Two marking methods have been 

 reported for age-0 red drum, Sciae- 

 nops ocellatus: 1) spray paint mark- 

 ing, 1 and 2) coded wire microtags 

 (Bumguardner et al., 1992). Fluo- 

 rescent staining is another method 

 that may be useful for age-0 S. 

 ocellatus and has been successfully 

 applied to juvenile red sea bream, 

 Pagrus major (Tsukamoto et al., 

 1989), and to larval and juvenile 



striped bass, Morone saxatilis (Secor 

 et al., 1991a). However, it is not 

 possible from these studies to de- 

 termine the most useful marking 

 method for age-0 S. ocellatus. 

 Hence, we examined mortality, 

 mark retention, and growth in age- 

 S. ocellatus that were marked by 

 one of six different methods: 1) 

 coded wire microtags, 2) external 

 plastic minitags, 3) alizarin com- 

 plexone, 4) oxytetracycline dihydrate 

 [OTC], 5) red fluorescent spray paint, 

 and 6) green fluorescent spray paint. 



Materials and methods 



We marked 614 cultured age-0 S. 

 ocellatus (mean standard length [SL] 

 ± standard deviation [SD]=67.4 ± 8.7 

 mm; range=48— 95 mm SL) on 4—5 

 February 1993. Fish were anesthe- 

 tized with tricane methanol sulfate 

 (50 mg MS222/L seawater), weighed, 

 measured, and randomly assigned to 

 one of the following treatments: red 

 fluorescent paint (red), green fluo- 

 rescent paint (green), external plas- 

 tic tags (plastic), binary coded wire 

 microtags (wire), oxytetracycline- 

 dihydrate (250 mg OTC/L 25 ppt sea- 

 water for 15 h), and alizarin-complex- 

 one (250 mg alizarin/L 25 ppt sea- 

 water for 15 h). 



Wire tags were injected into the 

 left epaxial muscle with a specially 

 designed hypodermic needle (North- 

 west Marine Technology, Shaw Is- 

 land, WA). The plastic tags (num- 



bered disk: 0.5x3x7 mm) were at- 

 tached posterior to the dorsal fin 

 with elastic thread sewn through 

 the left and right epaxial muscles. 

 Red and green paints were applied 

 at a pressure of 70 to 100 psi from 

 a distance of 30 to 50 cm (Phinney 

 et al., 1967). Atotal of 614 fish were 

 marked and classified as follows: 

 100 OTC, 114 alizarin, 100 red, 100 

 green, 100 plastic, and 100 wire. All 

 fish were held in a 7,570-L closed 

 seawater system, and differentially 

 marked fish were separated by flow 

 through partitions. Ammonia, ni- 

 trite, and nitrate levels were con- 

 trolled with an oyster shell biologi- 

 cal filter (mean ± standard error 

 [SE]: NH 3 =0.018 ±0.003 ppm; 

 NO 2 =0.253 ± 0.047 ppm; N0 3 =47.4 

 ±1.9 ppm). Particulates were re- 

 moved with a sand filter. Salinity 

 was held constant by addition of 

 artificial seasalts or freshwater 

 (mean salinity ± SE=25.0 ± 0.2 ppt). 

 Temperature was held constant 

 with three 1,000-W heaters (mean 

 temperature ± SE=20.8 ± 0.2°C). 



Fish mortalities were counted 

 and removed daily for 68 days. All 

 fish were fed daily at 5% body 

 weight per day with Zeigler salmon 

 crumbles no. 2 pellet food (Zeigler 

 Bros. Inc., Gardners, PA). At 25, 48, 

 and 68 days, all fish from each 

 treatment were anesthetized, 

 weighed, measured, and food was 

 adjusted for growth to maintain the 

 daily 5% body weight ration. Red 

 and green paint marks were veri- 

 fied with an ultraviolet light (paint 

 was not visible under white light). 

 Fish were considered marked if at 

 least one granule of pigment was 

 observed. Also, when fish were 

 anesthetized and measured, we 

 randomly sacrificed 20 fish from 



* Contribution 8-944903 of the Alabama 

 Agricultural Experiment Station, Auburn 

 University, Mobile, Alabama 36615. 



1 McMichael, Robert H., Jr. Florida Depart- 

 ment of Natural Resources, St. Peters- 

 burg, FL. Personal commun., 1992. 



Manuscript accepted 29 August 1994. 

 Fishery Bulletin 93:191-195 (1995). 



191 



