Identification of the metazoan parasite fauna of the Yellowfin tuna, <i>Thunnus albacares</i> (Bonnaterre, 1788) (Scombridae) from off the coast of Sinaloa, in northwestern Mexico

The yellowfin, <i>Thunnus albacares</i> (Bonaterre), is one of the most important resources for commercial fisheries along the Mexican Pacific coast. The parasite fauna of this important marine resource has been documented in different regions across its global distributional range. However, few studies have been conducted on parasites of tuna populations in the Cortezian Marine Ecoregion (CME) in northwestern Mexico, despite the development of the fresh and frozen sushi/sashimi-grade tuna market in recent decades. Our study aimed at identifying the metazoan parasite fauna of <i>T. albacares</i> in the CME. Between 2023 and 2024, 17 individuals were studied for parasites before being processed. Parasites were collected and identified using morphological and molecular data. One hundred twenty-five metazoan parasites were collected, representing 10 species, including the monogeneans <i>Hexostoma thynni</i> (Delaroche, 1811) Rafinesque, 1815, <i>Neobenedenia girellae</i> (Hargis, 1955) Yamaguti, 1963, and <i>Capsala</i> sp., the digenean <i>Hirudinella ahi</i> (Pallas, 1774) Baird, 1853, the larval cestode <i>Heterosphyriocephalus tergestinus</i> (Pintner, 1913) Dallarés, Carrassón and Schaeffner, 2016, larval forms of the nematode <i>Anisakis typica</i> (Diesing, 1860) Baylis, 1920, the acanthocephalan <i>Rhadinorhynchus laterospinosus</i> Amin, Heckmann, and Ha, 2011, and three species of copepods, <i>Euryphorus brachypterus</i> (Gerstaecker, 1853), <i>Pseudocycnus appendiculatus</i> Heller, 1865 and <i>Brachiella thynni</i> Cuvier, 1830<i>. Anisakis typica</i> reached the highest prevalence of infection in our samples, and along with <i>R. laterospinosus</i>, it reached the highest mean intensity values. This study reports a species that represents a zoonotic risk (<i>A. typica</i>) and contributes to the understanding of the parasite diversity of commercially important fish in the CME.