Age and Growth of the Common Thresher Shark in the Western North Atlantic Ocean

Abstract

AbstractAge and growth estimates were generated for the Common Thresher Shark Alopias vulpinus in the western North Atlantic (WNA) using vertebral centra from 173 females and 135 males ranging in size from 56 to 264 cm FL. Assuming that vertebral band pairs were deposited annually, we estimated ages up to 22 years (228 cm FL) for males and 24 years (244 cm FL) for females. The growth of both sexes was similar until approximately age 8 (185 cm FL), after which male growth slowed. The growth of females slowed at a later age (∼age 12) than that of males. Relative goodness of fit for all candidate models supported the separate modeling of sexes. For males, von Bertalanffy growth parameters generated from the vertebral data using a set size at birth (81 cm FL) provided the best fit for the band counts (asymptotic length [L∞] = 225.4 cm FL; growth coefficient [k] = 0.17). For females, the standard three‐parameter von Bertalanffy growth model provided the best fit to the band counts (L∞ = 274.5 cm FL; k = 0.09; theoretical age at a length of zero [t0] = −4.82). These are the first growth parameters generated for Common Thresher Sharks in the WNA and can be used to make informed decisions for the management of this species.