Despite their importance as habitats of priority aquatic species for conservation measures, the fauna of volcanic crater lakes in Nicaragua is not fully characterized. To extend the characterization of its aquatic fauna, fish captures were made in the Masaya Lagoon using nets and hooks, in two different periods and in two different sites. Fish tissue analysis of three fish taxa captured was carried out for the identification and quantification of metazoan parasites in the Masaya Lagoon. This scientific paper reports the first record of Chavez’s sabalete, Dorosoma chavesi (Actinopterygii; Dorosomatidae), in the Masaya Lagoon, within the Masaya Volcano National Park, thus extending its natural range to western Nicaragua. The species is registered in the Red List of the International Union for Conservation of Nature (IUCN) as Near Threatened. In addition, this report presents the first record of the metazoan parasite Ascocotyle tenuicollis (Platyhelminthes; Heterophyidae) in the Masaya Lagoon. The species was found in the heart of Amphilophus cf. citrinellus and Hypsophrys nematopus (both Actinopterygii; Cichlidae). No metazoan parasites were found in the heart, mesentery, or intestinal tract of D. chavesi. It is recommended to implement protection and monitoring measures for species in high conservation status in the Masaya Lagoon. ; A pesar de su importancia como hábitats de especies acuáticas prioritarias para medidas de conservación, la fauna de las lagunas cratéricas volcánicas en Nicaragua no es completamente caracterizada. Para ampliar la caracterización de su fauna acuática, se realizaron capturas de peces en la Laguna de Masaya utilizando redes y anzuelos, en dos períodos diferentes y en dos sitios distintos. Se realizó un análisis de tejidos de peces de tres taxones de peces capturados, para la identificación y cuantificación de parásitos metazoarios en la Laguna de Masaya. Este artículo científico reporta el primer registro del sabalete de Chávez, Dorosoma chavesi (Actinopterygii; Dorosomatidae), en la ...