Length at life stages of the white shark Carcharodon carcharias in the western North Atlantic

Abstract

ABSTRACT: Length at life stages of the white shark Carcharodon carcharias is not well known for most of the 9 populations of this species, including in the western North Atlantic (WNA). We analyzed length and maturity data by sex for 87 white sharks with sizes ranging 138-501 cm total length (TL), captured, studied, and released by OCEARCH during 2012-2022, off the US and Canadian Atlantic coasts. A binary logistic regression was used to estimate the length-at-maturity (L₅₀) for the WNA white shark with a Bayesian statistical framework using a Markov chain Monte Carlo method for numerical integration. Different trials using noninformative and informative priors were tested. The posterior probability distribution for L₅₀, steepness of the model (φ), and 95% credible intervals (CI) of the logistic model for females were L₅₀ = 411.3 cm TL (CI: 390.8-432.6 cm TL) and φ = 10.5 (CI: 5.7-17.8) and for males were L₅₀ = 334.9 cm TL (CI: 321.2-348.2 cm TL) and φ = 7.5 (CI: 4.2-12.4). These L₅₀ values are somewhat smaller than previously reported sizes-at-maturity for both sexes of this species. An ordinal logistic regression allowed us to determine the probability of being in the various life stages (young-of-the-year, juvenile, and adult) at a particular size. Estimating the length at any life-history stage of white sharks along with age estimates is useful for determining the reproductive value of the population and ultimately for estimating the relative contribution (elasticity) of vital rates to population growth.