624 



Fishery Bulletin 93(4), 1995 



Table 2 



Length-length, length-weight, and otolith weight-age re- 

 gressions for tarpon, Megalops atlanticus, from South 

 Florida waters. TL = total length (mm), FL = fork length 

 (mm), SL = standard length (mm), WT = weight (kg), OWT 

 = otolith weight (g), and AGE= age in years. Sample fork- 

 length range for all length-length regressions was 106- 

 2,045 mm and for length-weight regressions was 102-2,045 

 mm; age range for the otolith weight-age regressions was 

 1-55 years for females and 1-43 years for males. Values in 

 parentheses are standard errors. 



y=a+hX 



0.999 



0.999 



0.999 



0.999 



0.999 



0.999 



0.997 



0.872 



0.886 



Of 1,231 otoliths processed for age estimation, 138 

 (11.2%) were judged unreadable by one or both read- 

 ers and were not assigned ages, and an additional 

 116 (9.4%) otoliths were rejected for having high 

 variation among readings (CV>12.16%); thus 977 

 (79.4%) otoliths were accepted for age estimates. Of 

 these 977 otoliths, 470 (48.1%) were from YOY tar- 

 pon. The length-frequency distribution offish whose 

 otoliths were rejected because they were unsuitable 

 for age estimation was not significantly different from 

 that of all fish whose otoliths were examined 

 (X 2 =12.4, df=19,P=0.86). 



Tarpon are long-lived; the oldest fish examined was 

 a 2,045-mm female estimated to be 55 years old. The 

 oldest male was 43 years old and had a length of 

 1,710 mm. Tarpon growth was rapid until an age of 

 about 12 years, after which growth slowed consider- 

 ably (Fig. 3). Likelihood-ratio tests showed a signifi- 



Month 

 Figure 2 



(A) Percentage (by month) of otoliths from young-of-the- 

 year and 1-year-old tarpon, Megalops atlanticus, that had 

 formed a first annulus. (B) Monthly mean marginal incre- 

 ment width and standard deviation for otoliths from young- 

 of-the-year and 1-year-old tarpon. 



cant difference in the overall von Bertalanffy growth 

 models for males and females (% 2 =122.70, df=3, 

 P<0.001, Table 3). Estimates of L^ (x 2 =51.31, df=l, 

 P<0.001) and#(5c 2 =4.48, df=l,P=o7o36) also differed 

 between the sexes, while t o was not significantly dif- 

 ferent (x 2 =0.28, df=l, P=0.58). Lengths at age pre- 

 dicted by the von Bertalanffy equation agreed with 

 the average observed lengths of both female and male 

 tarpon (Fig. 3). Predicted lengths at age of females 

 were greater than those of males for all ages greater 

 than 4 years (Table 4). 



