164 



Fishery Bulletin 102(1) 



useful as a method of verification ( Cailliet et 

 al., 1983). Although no specimens younger 

 than 2-years-old were caught (perhaps due 

 to the gear selection bias), the presumed 

 size at birth was about 60-65 cm ( Compag- 

 no, 1984), which is similar to the estimated 

 size in the present study (66.8 cm). Also, the 

 estimated L r value (270 cm), derived from 

 the back-calculated or observed VBGF is 

 close to the maximum size of 276 cm men- 

 tioned by Bigelow and Schroeder ( 1948), 280 

 cm off Cuba (Compagno, 1984), and 275 cm 

 byGarrick(1985). 



Mean observed length-at-age is gener- 

 ally higher than back-calculated mean 

 length-at-age (Bonfil et al., 1993; Lessa and 

 Santana. 1998), leading to lower values of 

 L a and higher values of K. However, in the 

 present study, although mean observed 

 length-at-age is higher than mean back-cal- 

 culated lengths, parameters derived from back-calculation 

 provided a lower L x and a higher A' value. Inconsistency of 

 the observed length-at-age set is attributed to the missing 

 values in for ages 0, 1, 13, 14, and 16. This led to a VBGF 

 which provided an unrealistic birth size of 90 cm and which 

 present a flatter shape than the back-calculated curve. 



Von Bertalanffy growth parameters generated from both 

 back-calculation and by the Fabens method were all consid- 

 ered suitable and were of the same magnitude. However, 

 taking into account 1 ) parameters close to those derived 

 for length-frequency analysis, and 2) the best statistical fit, 

 the back-calculated VBGF was chosen as best representing 

 growth in the species. 



Comparisions of biological features such as maturity 

 size and maximum sizes have been used for inferences in 

 growth and to explain differences between sexes (Natanson 

 et al., 1995; Natanson and Kohler, 1996; Lessa et al., 2000). 

 Tin' studied species shows a disparity of -15 cm in matu- 

 rity sizes between sexes (Hazin, et al., 2000), corresponding 

 to ~2 years. In addition, the largest specimen, for which 

 six was determined, was a 252-cm female and the largest 

 male was 248 cm. These disparities, however, did not bring 

 about differences in growth between sexes, as indicated by 

 results of both tests used. Such a result can be explained by 

 the number of juveniles used for age determination (-83' I 



Thus, the number of adults was not high enough to bring 

 about any differences in the growth equation although 

 differences frequently occur after maturity, caused by dif- 

 ferent growth rates between sexes (Natanson et al., 1995; 

 Sminkey and Musick, 1995). 



Assuming that the time elapsed between birth and the 

 band corresponding to age 1 is one year, the species grows 

 38% of its birth length during the first year. This growth 

 rate is close to that (50%) generally assumed (Branstetter 

 1990; Cortes, 2000). Furthermore, the estimated K value 

 falls within the range suggested by the first author, and 

 according to him, the night shark is a relatively fast grow- 

 ing species, presenting a life strategy similar to that of C. 

 falciformis, and apparently depending on rapid growth for 

 adequate neonate survival due to vulnerability to preda- 

 tion from large sharks. 



In summary, considering the increasing fishing effort 

 on the night shark as a targeted species and that catches 

 are mainly composed by juveniles (representing 74.7' i of 

 specimens in landings), we believe that the A'-selected 

 characteristics of the species (including late maturity, 

 long gestation period, and low fertility 1 should be taken 

 into account in determining the management of this 

 resource. Demographic analyses will be required for the 

 examination of consequences of current levels of exploi- 



