Carlson et al,: Life history and population dynamics of Carcharhinus isodon 



287 



Peterson and Wroblewski (1984) method ranged from 

 Q.122lyT for age-0 sharks to 0.850 for age-15 sharks. 



Productivities obtained through the density-dependent 

 method averaged 0.04 l/yr, (median 0.042, 95% confidence 

 limits: 0.024-0.054) for Z=1.5 M and 0.071/yr (0.073, 

 0.045-0.091) for Z=2 M (Fig. 6). Generation times ob- 

 tained through hfe table simulation averaged 6.96 yr (6.90, 

 6.13-8.01). Expressed as a percentage, fertihty elasticities 

 averaged 12.6% (12.6, 11.1-14.0), elasticities of juvenile 

 survival were 47.7% (48.9, 37.4-56.9), and those of adult 

 survival totaled 39.7% (38.9, 31.5-50.2). 



Productivities from the density-dependent method 

 averaged 0.038/yr (0.038, 0.023-0.052) for Z=1.5 M and 

 0.067/yr (0.068, 0.043-0.088) for Z=2 M (Fig. 6). Mean 

 generation lengths from life tables averaged 6.34 yr (6.32, 

 5.75-7.04), fertility elasticities averaged 12.1% (12.3, 

 4.3-12.8), juvenile survival elasticities were 46.2% (48.9, 

 35.1-59.4), and adult survival elasticities totaled 41.6% 

 (38.8,28.6-53.2). 



Discussion 



Scenario 2 Estimates of M for adults ranged from a 

 minimum of 0.174 obtained through the Peterson and 

 Wroblewski ( 1984) method to a maximum of 0.528 obtained 

 through the Jensen (1996) method based on K or, when 

 expressed as survivorship, from 0.840/yr to 0.590/yr All 

 other annual survivorship estimates for adults fell within 

 that range: 0.596/yrfor the Pauly ( 1980) method, and 0.607 

 and 0.732/yrfor the Jensen ( 1996) method based on ages at 

 maturity of 3.3 and 5.3 yr, respectively. Estimates of sur- 

 vivorship at age from the Peterson and Wroblewski ( 1984) 

 method ranged from 0.689/yr for age-0 sharks to 0.840/yr 

 for age- 10 sharks. 



Finetooth sharks exhibit age and growth characteristics 

 intermediate to those of sharks in the small coastal com- 

 plex (e.g. Atlantic sharpnose, blacknose, and bonnethead 

 shark) and those of some large coastal sharks, such as 

 the blacktip shark. For example, the bonnethead shark 

 (Sphyrna tiburo) has been reported to have K values of 

 0.28-0.69/yr, age at maturity of 2.0-2.4 yr, and longevity 

 of 6-12 yr (Parsons, 1993a; Carlson and Parsons, 1997). 

 Finetooth sharks displayed lower A' values (0.24-0.41/.vr), 

 and higher age at maturity (3.9-4.3 yr) and longevity (8-14 

 yr) estimates. These growth characteristics are closer to 

 those exhibited by the blacktip shark (Branstetter, 1987; 



