288 



Fishery Bulletin 101(2) 



Age at maturity 



^=^ 



Figure 4 



Estimated age composition for male and female finetooth sharks col- 

 lected in the northeastern Gulf of Mexico. 



400 



600 



800 



1 000 1 200 

 Total lengtti (mm) 



1400 



1600 



1800 



Figure 5 



The relationship between maturity and total length for male and female 

 finetooth sharks. Mean total length and proportion mature were plotted in 

 lieu of the binomial data for clarity. Size class intervals are 50 mm TL. 



Killam and Parsons, 19891 than to those from other small 

 coastal species (Table 3). 



The von Bertalanffy age and growth model based on 

 observed data appears to provide a sound estimate for this 

 population of finetooth sharks. The model was checked by 

 comparing parameters from the observed model with those 

 estimated by back calculation (Cailliet et al., 1986; Cailliet, 

 1990). For both methods, theoretical maximum length and 

 growth coefficients (K) were similar. Theoretical maxi- 

 mum length (1587 mm TL for females and 1352 mm TL 

 for males) matched well the empirical size of the largest 

 sharks in the study area (1498 mm TL and 1360 mm for 

 females and males, respectively). In addition, the average 

 percent error in aging (APE=6.8%) was low and within 

 the range of estimates provided in other studies that also 

 used sagittal secti(ms for aging (ranging from 3.0*^ for the 



oceanic whitetip shark, Carcharhiniis longirnanus [Lessa 

 et al., 19991 to 8.1^7 for the blacktip shark IWintner and 

 Cliff, 19951 ). The fairly high precision is probably a result 

 of good band readability and reader experience. 



All age estimates from growth band counts were based 

 on the hypothesis of annual growth band deposition. 

 Although attempts were made to verify annual band 

 deposition through marginal increment analysis, the pat- 

 tern was inconclusive because of the lack of samples from 

 November to March. However, the decrease in incremental 

 growth from June through October was not large enough to 

 indicate a double band formation (Natanson et al., 1995). 

 Annual winter mark formation has also been assumed in 

 other studies of subtropical species ( Branstetter and Stiles, 

 1987; Natanson et al., 1995; Carlson et al., 1999) where 

 the marginal increment analysis showed a pattern similar 



