Crabtree et al. : Age and growth of Megalops atlanttcus 



623 



cantly larger than males, which ranged from 203 to 

 1,884 mm in length (median=l,346 mm, upper 

 quartile = 1,467 mm, rc=203; Mann-Whitney [/-test, 

 P<0.001). The recreational harvest of tarpon in 

 Florida consisted principally of large fish. Among the 

 fish sampled from the recreational fishery, females 

 ranged from 1,193 to 2,040 mm in length (mean = 

 1,677 mm, SD=141.5, n=322) and were significantly 

 larger than males, which ranged from 901 to 1,884 

 mm in length (mean=l,447 mm, SD=130.2, rc = 125; 

 f-test, £=15.77, P<0.001). 



We examined OTC-marked otoliths from 18 tar- 

 pon (Table 1). Individuals showed increases in length 

 ranging from 95 mm in 20 months to 235 mm in 21 

 months. Otoliths from 12 fish ranging in age from 4 

 to 9 years showed the expected pattern of otolith 

 growth; one annulus had been formed per year. One 

 tarpon (specimen number 1549) showed little otolith 

 growth and formed no visible annuli while in captiv- 

 ity. Two tarpon (specimen numbers 1559 and 1566) 

 that were sacrificed in May, 21 months after OTC 

 injection, had lower annulus counts than expected. 

 Otoliths from these two fish showed little growth 



distally to the annulus during their first winter or 

 spring in captivity. Otoliths from three other tarpon 

 (specimen numbers 1137, 1548, and 1565) were prob- 

 lematic, and we were unable to estimate their ages. 

 Annuli on these otoliths were indistinct, and we 

 would have judged these otoliths to be unreadable 

 had they come from wild fish. Five of the six fish 

 whose otoliths were problematic were held in the 

 heated facility at SERF and the other one was held at 

 Mote Marine Laboratory. Otoliths from all six tarpon 

 held in the flow-through facility at Keys Marine Labo- 

 ratory had the expected pattern of one annulus per year. 

 Marginal-increment analysis of otoliths from YOY 

 and 1-year-old tarpon suggested that one annulus 

 formed each year. Young-of-the-year tarpon formed 

 an annual mark sometime between December and 

 May, and all YOY and 1-year-old tarpon otoliths had 

 formed a first annulus by June (Fig. 2A). Mean mar- 

 ginal increments showed a seasonal minimum dur- 

 ing April-June and a maximum in November (Fig. 

 2B). Marginal-increment analysis of older tarpon was 

 not possible because of the incomplete seasonal cov- 

 erage and limited sample sizes. 



