281 



Abstract— The life history and popu- 

 lation dynamics of the finetooth shark 

 {Carcharhinus inodon) in the north- 

 eastern Gulf of Mexico were studied 

 by determining age, growth, size-at- 

 maturity, natural mortality, productiv- 

 ity, and elasticity of vital rates of the 

 population. The von Bertalanffy growth 

 model was estimated as L,=1559 mm 

 TL (l-e-024 .(+2 071) for females and L,= 

 1337 mm TL (l-e""-" "*'39i) for males. 

 For comparison, the Fabens growth 

 equation was also fitted separately to 

 observed size-at-age data, and the fits 

 to the data were found to be similar The 

 oldest aged specimens were 8.0 and 8.1 

 vr, and theoretical longevity estimates 

 were 14.4 and 8.5 yr for females and 

 males, respectively. Median length at 

 maturity was 1187 and 1230 mm TL. 

 equivalent to 3.9 and 4.3 yr for males 

 and females, respectively. Two sce- 

 narios, based on the results of the two 

 equations used to describe growth, were 

 considered for population modeling and 

 the results were similar Annual rates 

 of survivorship estimated through five 

 methods ranged from 0.850/yr to 0.607/ 

 yr for scenario 1 and from 0.840/yr to 

 0..590/yr for scenario 2. Productivities 

 were 0.04 1/yr for scenario 1 and 0.038/ 

 yr for scenario 2 when the population 

 level that produces maximum sustain- 

 able yield is assumed to occur at an 

 instantaneous total mortality rate (Z) 

 equaling 1.5 M, and were 0.071/yr and 

 0.067/yr, when Z=2 M for scenario 1 

 and 2, respectively. Mean generation 

 time was 6.96 yr and 6.34 yr for sce- 

 narios 1 and 2, respectively. Elasticities 

 calculated through simulation of Leslie 

 matrices averaged 12.6% (12. 19^ for sce- 

 nario 2) for fertility, 47.7% (46.2% for 

 scenario 2) for juvenile survival, and 

 39.7% (41.6% for scenario 2) for adult 

 survival. In all, the finetooth shark 

 exhibits life-history and population 

 characteristics intermediate to those of 

 sharks in the small coastal complex and 

 those from some large coastal species, 

 such as the blacktip shark {Carcharhi- 

 nus limhatus). 



Life history and population dynamics of 

 the finetooth shark (Carcharhinus isodori) 

 in the northeastern Gulf of Mexico 



John K. Carlson 



Enric Cortes 



Southeast Fisheries Science Center 



National Marine Fishenes Service, NOAA 



3500 Delwood Beach Road 



Panama City, Florida 32408 



E mail acldress:|ohn. carlsonisinoaa.gov 



Dana M. Bethea 



Center for Manne Sciences and Technology 

 North Carolina State University 

 Department of Zoology 

 303 College Circle 

 Morehead City, NC 28557 



Manuscript accepted 31 May 2002. 



Manuscript received 23 January 2003 

 at NMFS Scientific Publications Office. 



Fish. Bull. 101:281-292 (2003). 



In 1993, a fishery management plan for 

 sharks (NMFS, 1993) was developed 

 for the management of shark popula- 

 tions in waters of the U.S. Atlantic and 

 Gulf of Mexico. Because species-specific 

 catch and life history information was 

 limited, sharks were grouped and 

 managed under three categories: large 

 coastal, small coastal, and pelagic, 

 based on known life history, habitat, 

 market value, and fishery characteris- 

 tics (NMFS, 1993). Sharks in the large 

 coastal grouping included relatively 

 large, slow-growing, and long-lived spe- 

 cies, whereas the small coastal complex 

 included relatively small, fast-growing, 

 and short-lived species of sharks. 



Generally, commercial fishermen 

 target and harvest sharks in the large 

 coastal complex (e.g. blacktip shark 

 {Carcharhinus limbatus) and sand- 

 bar shark {Carcharhinus plumheus)). 

 Small coastal sharks are usually taken 

 incidentally in numerous commercial 

 fisheries and are commonly discarded 

 or used for bait. More recently, with 

 the reductions in commercial quotas 

 for large coastal species since 1993 

 (NMFS, 1999), fishermen have been 

 increasingly targeting small coastal 

 sharks. Estimated commercial land- 

 ings of small coastal sharks increased 

 from 7 metric tons (t) dressed weight 

 in 1994 to 305 t dressed weight in 



1999. Estimated recreational catches 

 of small coastal sharks reached a peak 

 of 170,000 animals in 1998 (Cortes^). 

 Given the importance of small coastal 

 sharks as bycatch and their increasing 

 value in directed commercial and recre- 

 ational fisheries, it is important to ob- 

 tain current and accurate information 

 on their life history. This information 

 can then be used in population models 

 incorporating variation and uncer- 

 tainty in estimates of life-history traits 

 to predict the productivity of the stocks 

 and ensure that they are harvested at 

 sustainable levels. 



The finetooth shark (Carcharhinus 

 isodon ) is a moderate-size species of 

 the small coastal shark group found 

 in coastal waters of the northwestern 

 Atlantic Ocean from North Carolina 

 to Florida, throughout the Caribbean 

 Sea, and the Gulf of Mexico (Compagno, 

 1984; Castro, 1993). This species makes 

 up a significant portion of a directed 

 drift gillnet fishery operating off the 

 southeast U.S. coast (Trent et al., 1997; 



Cortes, E. 2000. 2000 shark evaluation 

 annual report. Sustainable Fisheries Divi- 

 sion contribution no. SFD-00/01-119, 23 p. 

 Southeast Fisheries Center, National Ma- 

 rine Fisheries Service, 3500 Delwood 

 Beach Rd., Panama City, FL 32408. 



