Abstract.- Otolith microstruc- 

 ture analysis was applied to sagittae 

 from 18 larvae (5-10mm notochord 

 length) and 77 juvenile, young adult, 

 and adult (4.3-212cm lower jaw fork 

 length, LJFL) Atlantic blue marlin 

 Makaira nigricans for estimation of 

 age and growth rate. Contingency 

 table analyses indicated that a peri- 

 odicity of one increment per day was 

 most consistent with the seasonal 

 distribution and peaks of back-calcu- 

 lated spawning dates of the aged 

 samples (May to November), and 

 with information on spawning re- 

 ported in the literature. Microstruc- 

 tural features of larval blue marlin 

 sagittae were indistinguishable from 

 those in the otoliths of other tropical 

 pelagic species where conclusive age 

 validation has verified daily incre- 

 ment deposition rates. Average per- 

 cent error of the counting method 

 (precision) for the aged samples of 

 juveniles and young adults/adults 

 was 1.6%. 



Estimated ages of larvae ranged 

 from 9 to 12 days while estimated 

 ages of juveniles, young adults, and 

 adults ranged from 21 to 495 days 

 (1.4 years). Otolith microstructure 

 analysis could not be applied with 

 confidence to blue marlin older than 

 1.4 years. Allometric equations for 

 the length-weight relationship of im- 

 mature (< 140 cm LJFL) and mature 

 male and female blue marlin (>140 

 cm) are presented. Sexual dimorphic 

 growth (weight only) in Atlantic blue 

 marlin appears to begin at 140 cm 

 LJFL. 



Both the maximum (~16mm/day 

 at 50 days) and sustained (~10mm/ 

 day) growth rates in length during 

 the first 100 days indicate that At- 

 lantic blue marlin are one of the fast- 

 est growing of all teleosts in the 

 early stages of development. An at- 

 tempt to determine the periodicity of 

 presumed annual marks on otoliths 

 from adult blue marlin (213-367 cm 

 LJFL) by evaluating microstructural 

 characteristics and increment counts 

 between annuli was unsuccessful. 



Estimating Age and Growth of 

 Young Atlantic Blue Marlin 

 Makaira nigricans from 

 Otolith Microstructure 



Eric D. Prince 

 Dennis W. Lee 

 James R. Zweifel 



Miami Laboratory. Southeast Fisheries Science Center 



National Marine Fisheries Service, NOAA 



75 Virginia Beach Drive. Miami, Florida 33149-1099 



Edward B. Brothers 



EFS Consultants, 3 Sunset West, Ithaca, New York 14850 



Published reports on age determina- 

 tion for billfishes (Istiophoridae) are 

 rare compared with those available 

 for other fishes (Lee 1989). More- 

 over, data providing validated ages 

 for this family are almost nonexis- 

 tent (Prince et al. 1987), yet age and 

 growth data are important for stock 

 assessment of fish populations 

 (Beamish and McFarlane 1983). 



Age determination of Atlantic blue 

 marlin Makaira nigricans is prob- 

 ably more difficult than for most 

 other teleosts because of numerous 

 aspects of the marlin fishery and 

 their life history, including the facts 

 that (1) their life cycle does not lend 

 itself to artificial propagation or sur- 

 vival in captivity, (2) they are a very 

 large, highly mobile, solitary, com- 

 paratively rare, and sparsely distrib- 

 uted predator with an extensive 

 geographical range, making them in- 

 accessible for routine scientific study 

 and increasing the costs and diffi- 

 culty of obtaining samples, (3) they 

 occupy different climatic areas dur- 

 ing the same calendar year, making 

 interpretations of bands on hard 

 structures less certain because they 



Manuscript accepted 13 February 1991. 

 Fishery Bulletin, U.S. 89:441-459 (1991). 



•Contribution MIA-90/91-38, Southeast Fish- 

 eries Science Center, National Marine Fish- 

 eries Service, NOAA. 



may not form with great regularity 

 or uniformity, (4) while incidental 

 catches from longline fisheries form 

 the largest part of their harvest, the 

 logistics of sampling longline opera- 

 tions have hindered collection and ex- 

 amination of large numbers for scien- 

 tific study, (5) in comparison with 

 almost all other teleosts, their oto- 

 liths are exceptionally small and fra- 

 gile, making them difficult to extract 

 and expensive to prepare and ana- 

 lyze, (6) specimens less than 34 kg 

 (751b) are extremely rare, due in part 

 to the apparent exceptionally rapid 

 growth rate in juveniles, (7) extreme- 

 ly low tag-recapture rates (0.4% in 

 the Atlantic; Scott et al. 1990) make 

 acquisition of hard structures from 

 long-term recaptures or oxytetra- 

 cycline injected blue marlin highly 

 unlikely, and (8) long-lived species 

 are more difficult to age and prelim- 

 inary indications suggest that blue 

 marlin are long lived, attaining ages 

 of 25-30 years or more (Hill et al. 

 1989). 



Recognizing these difficulties, the 

 National Marine Fisheries Service's 

 (NMFS) Southeast Fisheries Science 

 Center (SEFSC) began a long-range 

 plan in 1980 to collect samples for 

 age determination and an evaluation 

 of ageing methods of blue and white 



441 



