fish, even though critical to resource management, 

 is limited. 



Age estimates and growth rates are necessary to 

 prepare accurate stock statistics. Age determina- 

 tions in fish are generally indirect measures and 

 are made from length-frequency analyses (Peter- 

 sen's method) or annual events in hard tissue (Ba- 

 genal 1974). The length-frequency method has 

 been applied to sailfish (de Sylva 1957; Koto and 

 Kodama 1962), but the results are inconclusive at 

 best. Annual events recorded in hard tissues are a 

 more accurate method of age determination, and 

 Jolley (1974, 1977) counted the rings in dorsal fin 

 spines to estimate the age of sailfish. The length- 

 frequency data (de Sylva 1957; Koto and Kodama 

 1962) and proposals of Maksimov (1971) from 

 length-frequency data indicated a rapid growth 

 rate and relatively short lifespan of 3-5 yr for a 

 sailfish. Jolley 's (1974) analysis also indicated a 

 rapid growth rate but a possible lifespan of about 

 10 yr, so at present, age determination in sailfish is 

 unresolved. 



Otoliths have been shown to be accurate indi- 

 cators of age (Bagenal 1974; Six and Horton 1977) 

 and are particularly useful on species offish which 

 lack scales or have minute scales such as those 

 species in the family Istiophoridae. Otoliths are 

 composed of calcium carbonate in the form of 

 aragonite (Irie 1955; Degens et al. 1969) and are 

 formed in the labyi'inth of teleost fish. There are 

 three otoliths (sagitta, lapillus, and asteriscus) on 

 each side of the brain cavity in the inner ear (Low- 

 enstein 1971) and the morphology of these calcified 

 structures is species specific (Hecht 1978; Morrow 

 1979). The sagitta is usually the largest otolith 

 and the one most often used for age determina- 

 tions, but the other two otoliths have not been 

 adequately studied and might also be of use. The 

 otoliths of sailfish and other billfishes (families 

 Istiophoridae and Xiphiidae) have been thought to 

 be so small that they would not be useful in age 

 determinations (Jolley 1974; Beckett 1974). 

 Consequently, age and gi-owth data are lacking for 

 these important recreational and commercial 

 species. In this study we analyzed 65 sailfish and 

 described the morphology of the otoliths. A 

 mathematical relationship between the wet 

 weight of the fish and morphological features of 

 the sagitta, enabled us to estimate the age of all 

 but one specimen. Ages of very large fishes, previ- 



'Contribution No. .397 of the Belle W. Baruch Institute for 

 Marine Biology and Coastal Research. University of South 

 Carolina. 



ously difficult to measure, were readily amenable 

 to otolith age analysis. 



Methods 



Otoliths were collected from sailfish at taxi- 

 dermy facilities in Florida in fall 1978. Total 

 lengths (TL) and wet weights were recorded from 

 the tags placed on the fish at the dock and otoliths 

 were extracted from 65 fish. The otoliths of sailfish 

 were extremely small and required careful dissec- 

 tion. A saggital cut was made on the midline of the 

 head and the semicircular canals dissected from 

 the brain area. All three otoliths were removed 

 from the semicircular canals and cleaned. Dried 

 otoliths were attached to aluminum stubs; gold- 

 coated otoliths were viewed in a Cambridge 

 Stereroscan Mark 2A scanning electron micro- 

 scope (SEM). 



The internal structure of the sagitta was ob- 

 served by attaching the sagitta to a SEM stub with 

 5 min epoxy and fracturing it through the core 

 region. The fractured otoliths were etched for 5 

 min in 79c ethyl enediaminetetraacetic acid (pH 

 7.4) and then coated with gold before viewing. The 

 lapilli of sailfish were viewed with reflected light 

 microscopy to determine if this would be a viable 

 alternative to SEM preparations. 



Results 



The morphological nomenclature we use to de- 

 scribe sagitta is that of Hecht (1978) and Morrow 

 ( 1979). The otoliths are extremely small, from 0.75 

 to 1.5 mm long. The medial or concave surface 

 (Figure 1) has a deep and well-defined sulcus and 

 the depth of the sulcus increased with fish weight. 

 The sagitta has no collum and lacks anterior and 

 posterior cristae. The excisural notches are dis- 

 tinct and V-shaped and have two lobes which fold 

 onto each other. The antirostrum is one-third as 

 long as the rostrum and well separated from the 

 rostrum. Consequently sagitta had a different 

 configuration from most sagitta, as the rostrum is 

 exaggerated. The surface of the concave portion of 

 the sagitta is granular with crystalline palisade 

 configurations. 



There are distinct ridges on the side of the rostral 

 lobe (Figure 2) which we interpret as annual 

 events, as there is an increase in ridge number 

 with weight (Figure 3). The sagitta of a sailfish 



'^Reference to trade names doesnot imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



361 



