Age and growth of the blacknose shark, <Emphasis Type="Italic">Carcharhinus acronotus</Emphasis>, in the western North Atlantic Ocean with comments on regional variation in growth rates |
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Authors: | William Driggers John Carlson Brian Cullum John Dean Doug Oakley |
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Institution: | (1) Belle. W. Baruch Institute for Marine Biology and Coastal Research, University of South Carolina, SC, U.S.A;(2) National Marine Fisheries Service, Southeast Fisheries Science Center, Mississippi Laboratories, MS, U.S.A;(3) National Marine Fisheries Service, Southeast Fisheries Science Center, Panama City Laboratory, 3500, Delwood Beach Rd., FL, U.S.A;(4) Marine Resources Division, South Carolina Department of Natural Resources, 217 Ft. Johnson Rd., SC, U.S.A |
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Abstract: | We examined the age and growth of the blacknose shark, Carcharhinus acronotus, in the western North Atlantic Ocean by obtaining direct age estimates using vertebral centra. We verified annual deposition of growth increments with marginal increment analysis and validated it by analyzing vertebrae marked with oxytetracycline from a female blacknose shark held in captivity. Von Bertalanffy growth parameters indicated that female blacknose sharks have a lower growth constant (k), a larger theortical maximum size (L), and are longer lived than males. We compared these growth parameters for blacknose sharks in the western North Atlantic Ocean to growth parameters for blacknose sharks collected in the eastern Gulf of Mexico to test for differences between regions. Females in the western North Atlantic Ocean have a significantly lower L, lower k, and a higher theoretical longevity than females in the Gulf of Mexico. Males in the western North Atlantic Ocean have a higher L<>, lower k, and higher theoretical longevity than males in the Gulf of Mexico. The significant differences between these life history parameters for blacknose sharks suggest that, when possible, future management initiatives concerning blacknose sharks should consider managing the populations in the western North Atlantic and the Gulf of Mexico as separate stocks. |
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Keywords: | life history Carcharhinidae small coastal shark elasmobranch |
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