196 



Fishery Bulletin 101(1) 



San Mateo, CA, making a total of 120 re- 

 captured leopard sharks from the original 

 1979 tagging. The tag number was readable 

 and traceable back to the tagging date (23 

 August 1979) and length (87 cm TL), which 

 was compared with the recapture length 

 (119.4 cm TL) and date. This individual 

 exhibited an average annual growth of only 

 1.47 cm/yr, but its recapture length for its 

 presumed age (30) was also close to that 

 predicted by the Kusher et al. (1992) as- 

 ymptotic FISHPARM VBGF for tagged and 

 recaptured leopard sharks. 



Discussion 



The tagging and recapture of fish whose 

 calcified structures have been marked 

 with the calcium-labeling fluorophor OTC 

 offer a simple and conclusive method for 

 establishing the timing of gi'owth zone for- 

 mation in these structures. Validating the 

 timing of centrum or spine band formation 

 is especially important for elasmobranchs 

 as a group because, unlike teleosts, the 

 assumption of annual deposition of band 

 pairs has not been confirmed for many spe- 

 cies and has been challenged for some. It 

 has been suggested that two band pairs are 

 deposited annually in the basking shark, Cetorhinus 

 maximus (Parker and Stott, 1965) and the shortfin 

 mako shark, Isur-us oxyrinchiis (Pratt and Casey, 

 1983), although validation is still pending for these 

 species. Furthermore, Natanson (1984) and Natan- 

 son and Cailliet (1990), working with OTC-injected 

 Pacific angel sharks, Squatina californica, found no 

 correlation between centrum band deposition and 

 any temporal cycle and concluded that bands were 

 deposited in response to somatic growth. Nevertheless, 

 elasmobranchs for which the deposition of one band 

 pair per year has been established and validated with 

 OTC (for at least selected size and age classes) include 

 the thornback ray, Raja clavata, (Holden and Vince, 

 1973; Ryland and Ajayi, 1984); R. microocellata and 

 R. mniitagui (Ryland and Ajayi, 1984); Raja erinacea 

 (Natanson, 1993); Bathyraja sp. (Gallagher and Nolan, 

 1999); lemon shark, Negapriou hrevirostris (Gruber 

 and Stout, 1983; Brown and Gruber, 1988); spiny 

 dogfish, Squalus acarithias (Beamish and McFarlane, 

 1985;Tucker 1985) leopard shark, Triakis semifasciata 

 (Smith, 1984; Kusher et al., 1992); neonate sharpnose, 

 Rhizoprionodon terraenovae, and sandbar, C. plumbeus, 

 sharks (Branstetter 1987); and bonnethead shark, 

 Sphyrna tihuro (Parsons 1993). 



By demonstrating the persistence of OTC in the min- 

 eralized tissue of a cartilaginous fish at liberty for nearly 

 two decades, our study confirms the long-term effective- 

 ness of this age validation tool. The number of band pairs 

 conformed to the number of years at liberty, although 



Figure 2 



Enlargement of photomicrograph of a transverse vertebral section of a 

 leopard shark iTriakis semifasciata) showing years (abbreviated in figure) 

 that correspond to annuli distal to the tetracycline mark at year 1979 on 

 the corpus calcareum. 



bands near the centrum periphery appeared in some sec- 

 tions to be absent or incompletely formed, even after care- 

 ful embedding and sectioning. This emphasizes the impor- 

 tance of interpri'ting bands nearest the growing margin 



