Validation of annulus formation and growth estimation of South Atlantic swordfish

Abstract

Swordfish (Xiphias gladius) is heavily exploited in the Atlantic Ocean by several European fleets and age and growth studies are essential for the accomplishment of the stock assessments carried out by ICCAT. The present study aims to validate the periodicity of growth increments on swordfish fin spines and provide first estimates of the growth parameters of South Atlantic swordfish. A total of 502 (231 males and 271 females) spine samples were collected from swordfish specimens onboard commercial longline vessels, from 2006 to 2009. Estimated ages ranged between 0 and 12 years, with age groups 3 and 4 dominating the samples. Marginal increment analysis suggested that growth bands were deposited annually in mid-spring. Fitted standard von Bertalanffy growth parameters (sexes combined) were L∞ = 317.133, k = 0.085 and t0 = −2.488. Minor, but insignificant, growth differences were observed between sexes.