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Reproductive cycle of the blacknose shark Carcharhinus acronotus in the Gulf of Mexico

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Abstract:

The reproductive periodicity of blacknose sharks Carcharhinus acronotus in the northern Gulf of Mexico was determined by examining reproductive tissues from specimens collected monthly from 2002 to 2005. Monthly changes in shell gland mass, right ovary mass and ovarian follicle diameter were assessed for 74 mature females. Temporal changes in testes mass, testes width and proportion of mature spermatocysts were examined for 64 mature males. Trends in female reproductive tissues suggested an annual peak in reproductive activity during June and July, while trends in male variables suggested an annual reproductive peak during May and June. Although male and female reproductive activity peaked in different months, a strong synchronicity existed between the proportion of mature spermatocysts and the diameter of the largest ovarian follicle. Based on these results, the mating season of blacknose sharks lasts from mid-May to July in the Gulf of Mexico. Maximum embryo sizes were observed in May, which suggested that partition occurs during late May or early June. Results indicate that blacknose sharks have a clearly defined annual cycle in the Gulf of Mexico. This conclusion is further supported by the complete absence of gravid females without vitellogenic ovarian follicles among all mature females examined.

Keywords: Carcharhinidae; blacknose shark; elasmobranch; reproduction

Document Type: Regular Paper

DOI: https://doi.org/10.1111/j.1095-8649.2007.01314.x

Affiliations: 1: National Marine Fisheries Service, Southeast Fisheries Science Center, Mississippi Laboratories, P. O. Drawer 1207, Pascagoula, MS 39568, U.S.A. 2: Florida Program for Shark Research, Florida Museum of Natural History, University of Florida, P. O. Box 117800, Gainesville, FL 32611, U.S.A. 3: National Marine Fisheries Service, Southeast Fisheries Science Center, Panama City Laboratory, 3500 Delwood Beach Road, Panama City, FL 32408, U.S.A.

Publication date: 2007-02-01

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