Life History of Swordfish, Xiphias gladius, Caught in the Northern Gulf of Mexico

Abstract

The current study examined 93 Swordfish, Xiphias gladius, (64 females, 27 males, 2 unknown) ranging in size from 77.6–246.3 cm lower jaw fork length (LJFL) from the northern Gulf of Mexico (GOM). Samples were collected between March and August in 2005–2007, 2017–2019 and 2021. Age estimates of 51 Swordfish resulted in a maximum observed age of 11 years (205.0 cm LJFL) and 7 years (190.4 cm LJFL) for females and males, respectively. Observed and back—calculated length—at—age data were fitted to 4 growth models (2— and 3— parameter von Bertalanffy, Gompertz, and logistic). The 2—parameter von Bertalanffy was the model that best fit the data (Linf = 210.2 cm LJFL, k = 0.25). Histological examination of gonadal tissue from 91 fish indicated that females reached 50% and 95% physiological maturity at 116 ± 6 cm LJFL and 143 ± 8 cm LJFL, respectively, corresponding to ages 2—3 years. All males >82 cm LJFL were physiologically sexually mature. Only 10% of females were reproductively active, with spawning capable females captured in June. Reproductively active females exhibited asynchronous oocyte development indicating batch spawning. Most males (96%) were spawning capable from April–August. Philometra sp. infection was found in all ovaries examined (n = 16) but with low abundance (2.25 ± 0.42); male philometrids were more prevalent than females (91.7% and 66.7%, respectively). Swordfish in the northern GOM appear to achieve sexual maturity at a younger age, grow faster, and have shorter theoretical longevity than previous reports from other regions world—wide.