Age, growth, maturation and diet of the Finetooth Shark, Carcharhinus isodon, in the coastal waters of the western North Atlantic Ocean

Loading...
Thumbnail Image
Date
Authors
Vinyard, Elizabeth Anne
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
<p>Age, growth, maturity, and diet were examined for Finetooth Sharks, <em>Carcharhinus isodon</em>, in coastal waters of the western North Atlantic Ocean (WNA) from Winyah Bay, South Carolina to Cape Canaveral, Florida. Ages were estimated from the vertebrae of 190 males and 218 females. The maximum observed age for males and females was 21.9 years and 22.3 years, respectively. Sizes ranged from 376 mm to 1174 mm FL for males and 380 mm to 1282 mm FL for females. Significant differences were detected between the sexes necessitating sex-specific von Bertalanffy growth models. These models yielded the following parameters: male, <em>L<sub>&infin;</sub></em> = 1141mm FL, <em>k</em> = 0.279, <em>L<sub>0</sub></em> = 461 mm FL; female, <em>L<sub>&infin;</sub></em> = 1257mm FL, <em>k</em> = 0.197, <em>L<sub>0</sub></em> = 463 mm FL. Median length (<em>L<sub>50</sub></em>) and age (<em>A<sub>50</sub></em>) at maturity was 1006 mm FL for males and 1041 mm FL for females corresponding to 6.6 years and 6.9 years, respectively. Significant differences in growth and maturity were detected between the current study and previously published parameters for the WNA and Gulf of Mexico (GOM). Stomach contents (<em>n</em> = 230) confirmed a teleost diet for all age categories (YOY, 99.8% Index of Relative Importance (IRI), juveniles, 99.8% IRI; adults, 99.9% IRI) with <em>Brevoortia tyrannus</em> as the most important prey species. Stable isotope analyses (<em>n</em> = 58) indicated juveniles had a significantly greater reliance on pelagic carbon sources while adults had significantly higher nitrogen ratios indicative of higher trophic level feeding. While dietary overlap between age categories was observed, each category maintained unique isotopic niche space. Juveniles had the smallest combined percentage of dietary niche overlap while adults had the largest. Results from the current study, in conjunction with previously published reproductive, tag-recapture and genetic studies, suggest separate stocks in the WNA and GOM.</p>
Description
Keywords
Citation