Abstract

Swordfish, Xiphias gladius, is a highly migratory pelagic species found circumglobally in tropical, subtropical and temperate ocean waters. Historically, studies investigating age, growth and reproduction of swordfish have primarily been conducted on specimens collected from commercial fisheries in the Atlantic and Pacific Oceans and the Mediterranean Sea, with information lacking from the Gulf of Mexico (GOM). Increased recreational fishing for swordfish in the northern GOM dictates the need to collect regional life history data to inform future stock assessments in support of effective management of swordfish populations in the GOM. The current study collected biological samples and data from 51 swordfish (45 females and 6 males) ranging in size from 82.6 – 246.3 cm lower jaw fork length that were landed in the northern Gulf of Mexico recreational fishery during 2017, 2018, and 2019. Histological examination of gonadal tissue from an initial subset of 26 fish indicated that all had reached sexual maturity and all males were spawning capable. Sixty percent of female swordfish were in the early developing reproductive phase, while 10% were in the spawning capable phase. Additionally, females exhibited asynchronous oocyte development indicating batch spawning. The second anal spine of each specimem was prepared for age analysis. Independent readers provided annuli count with no prior knowledge of specimen size, sex, or previous counts. Age estimates ranged between 3 - 11 years. Back-calculations of age were conducted to model growth due to limited sample size and resulting values fitted to four growth models (two- and three-parameter von Bertalanffy, Gompertz, and logistic). To our knowledge this ongoing study is the first to investigate life history of recreationally landed swordfish in the GOM.

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