Age and Growth of the Blacknose Shark, Carcharhinus acronotus, in the Eastern Gulf of Mexico

Abstract

Age and growth of the blacknose shark, Carcharhinus acronotus, from the eastern Gulf of Mexico was estimated by counting bands on the vertebral centra from 123 individuals. Back-calculated von Bertalanffy growth functions were constructed for populations in northwest Florida and Tampa Bay, Florida. Von Bertalanffy growth function parameters for males in northwest Florida (L, = 963.1 mm FL, K = 0.59, to = -0.754 yr) were significantly different from those in Tampa Bay (L, = 801.0 mm FL, K = 0.771, to = -0.797 yr), as were those for females (L, = 1136.5 mm FL, K = 0.352, to = -1.212 yr in northwest Florida; L, = 1241.3 mm FL, K = 0.237, to = -1.536 yr in Tampa Bay). Theoretical longevity, estimated as the age at which 95% of L, is reached, varied from age 10-16 yr for females and 4.5-9.0 yr for males, depending on geographic area. The oldest sharks aged were 4.5+ yr. Centrum edge and marginal increment analyses lent support to the hypothesis that narrow dark bands are formed during winter months. Length-frequency analysis verified back-calculated size at ages 0, 1, and 2. The growth dynamics of blacknose sharks are similar to those of other relatively small, fast-growing, short-lived species of sharks.