160 



Fishery Bulletin 102(1) 



fish in the early years to be systematically lower than 

 younger ones at the same age (Lee's phenomenon) was 

 not evident (Tables 1 and 2). 



Using back-calculated lengths-at-age (Table 3), we 

 plotted male and female growth curves separately and 

 then tested the data; no indication of significant differ- 

 ences in growth was observed between sexes with both 

 the Kapenman's (P>0.05) and likelihood ratio tests 

 (Table 4). Data were then treated together, incorporat- 

 ing individuals of undetermined sex. VBGFs derived 

 from observed length at age were not tested because 

 of missing values in different age classes. The method 

 of Fabens for combined sexes, fitted to back-calculated 

 data, provided L, and K, by using b = 0.781, L = 62.5 

 cm (Compagno, 1984) and. At = 1 year (Table 2). 



Parameters from back-calculation were close to 

 those derived from length-frequency analysis for 1055 

 specimens, whereas observed lengths and the Fabens 

 method, provided the most varying parameters with 

 lowest correlation and highest coefficients of variation 

 (Table 2). 



The smallest specimen in the vertebral sample show- 

 ing two complete bands in sections was 111.5 cm, close 

 to the estimated mean back-calculated length at age 

 two of 113.7 cm (Table 3). Size at maturity, 185-190 cm for 

 males and 200-205 cm for females, corresponded to 8- and 

 10-year-old individuals, respectively (Fig. 6). The largest 

 and oldest specimen whose vertebrae were used, was 242 

 cm, which corresponded to 17-year-old individual. 



A growth rate of 25.4 cm/yr was estimated from birth to 

 the first band — a rate that corresponded to 389 of the birth 



M A 



J J 

 Month 



Figure 4 



Categorization of edges by month for the night shark iC. 

 signal its) off northeastern Brazil. 



length (the length at birth being 66.8 cm). Also, a mean rate 

 of 8.55 cm/yr was calculated for 8- to 10-year-old individu- 

 als, when maturity is achieved (Table 3). 



Considering mature individuals >185 cm. the age com- 

 position for the vertebral samples («=317) indicated that 

 17.3% of specimens were adults (Table 5). Instead, for the 

 total sample (ra=1055), where the age ranged between 2 to 

 al7 years, adults corresponded to 25.3% of the total sample 



