LONGEVITY AND AGE VALIDATION OF A TAG-RECAPTURED 



ATLANTIC SAILFISH, ISTIOPHORUS PLATYPTERUS, 



USING DORSAL SPINES AND OTOLITHS 



Eric D. Prince, 1 Dennis W. Lee, 1 Charles A. Wilson, 2 

 and John M. Dean 3 



ABSTRACT 



A tagged female Atlantic sailfish, Istiophorus platypterus, of 24.6 kg (54 lb) was recaptured on 14 January 

 1984, after being at large for 10 yr and 10 mo (4,025 d). Approximate age based on tagging records 

 ranged from at least 13 to 15 + yr. Maximum estimated longevity of this species was therefore revised 

 upwards from previously reported >7 yr to at least 13-15+ yr. Estimates of age based on sections of 

 dorsal spine numbers 3-6 ranged from 2 to 8 yr and substantially underestimated the range in age known 

 from tagging records (13-15 + yr). This discrepancy was due to enlargement of the porous, vascularized 

 core of spine sections which obscured zonations associated with early growth history. Thus, dorsal spines 

 do not appear to be useful in ageing older sailfish (i.e., >5 yr). Age estimates from sagittae (otoliths) 

 were 13 yr based on scanning electron microscope counts of external ridges and analysis of internal otolith 

 microstructure. Otolith age, therefore, agreed with age known from tagging records. The relatively large 

 size of the sagitta (7.84 mg) also provides additional evidence that the otolith could be from a very old 

 sailfish. These data strongly suggest that in older, larger sailfish (>5 yr, 22.7 kg), sagittae, rather than 

 dorsal spines, should be used as the source of age and growth information. 



The Atlantic sailfish, Istiophorus platypterus, is one 

 of the most popular recreational fishes along the 

 U.S. Atlantic coast, Gulf of Mexico, and Caribbean 

 Sea. In fact, this species has been described as the 

 most sought after fish by southeast marine charter 

 boat anglers, particularly in south Florida (Ellis 

 1957). Although most landings of Atlantic sailfish 

 in the southeastern United States are made by 

 recreational anglers, many are also taken inciden- 

 tally by domestic and foreign commercial longline 

 vessels (Lopez et al. 1979). The biological informa- 

 tion presently used in stock assessments of Atlan- 

 tic sailfish (Conser 1984) consists of age and growth 

 data derived exclusively from analysis of dorsal 

 spines (Jolley 1974, 1977; Hedgepeth and Jolley 

 1983). However, uncertainties remain concerning 

 Atlantic sailfish age structure, longevity, choice of 

 skeletal structure for ageing, and rate of growth 

 because of inconsistencies reported in the literature. 

 In addition, the accuracy of age and growth esti- 



1 Southeast Fisheries Center Miami Laboratory, National Marine 

 Fisheries Service, NOAA, 75 Virginia Beach Drive, Miami, FL 

 33149-1099. 



2 BeIle W. Baruch Institute for Marine Biology and Coastal 

 Research, Department of Biology and Marine Science Program, 

 University of South Carolina, Columbia, SC 29208; present ad- 

 dress: Coastal Ecology and Fisheries Institute, Louisiana State 

 University, Baton Rouge, LA 70803-7503. 



3 Belle W. Baruch Institute for Marine Biology and Coastal 

 Research, Department of Biology and Marine Science Program, 

 University of South Carolina, Columbia, SC 29208. 



mates from skeletal structures and length-frequency 

 analyses have not been validated for all age classes 

 (de Sylva 1957; Jolley 1974, 1977; Radtke and Dean 

 1981; Hedgepeth and Jolley 1983). 



One problem in using spines as a source of age 

 and growth information is the tendency of the 

 vascularized core to obscure zonations associated 

 with early growth history. The enlargement of the 

 vascularized core and subsequent reabsorption of 

 tissues are most severe in the largest and oldest 

 specimens (causing underestimates of true age) and 

 have contributed to the lack of detailed information 

 for older age classes. Several studies have also 

 reported difficulty in interpreting the double and tri- 

 ple bands often observed in Atlantic sailfish spines 

 (Jolley 1977; Hedgepeth and Jolley 1983). These 

 problems are not unique to sailfish (Casselman 1983; 

 Compean- Jimenez and Bard 1983) and have resulted 

 in an unusually large proportion of spine samples 

 (as much as 76%) being rejected for age and growth 

 analysis (Jolley 1977). Radtke and Dean (1981) 

 reviewed this problem and suggested that otoliths 

 (sagittae) may be a better skeletal structure for age 

 and growth assessment in sailfish because these 

 structures do not have the disadvantages associated 

 with the spinal core. For example, 98% of the oto- 

 lith samples examined by Radtke and Dean (1981) 

 were reportedly suitable for age and growth estima- 

 tion. Even though these preliminary findings were 



Manuscript accepted October 1985. 



FISHERY BULLETIN: VOL. 84, NO. 3, 1986. 



493 



