Neves, AnaSequeira, VeraVieira, Ana RitaSilva, ElisabeteSilva, FredericaDuarte, Ana MartaMendes, SusanaGanhão, RuiAssis, CarlosRebelo, RuiMagalhães, Maria FilomenaGil, Maria MGordo, Leonel Serrano2023-08-252023-08-252022Neves A, Sequeira V, Vieira AR, Silva E, Silva F, Duarte AM, Mendes S, Ganhão R, Assis C, Rebelo R, Magalhães MF, Gil MM, Gordo LS. 2022. Reproduction of the blue jack mackerel, Trachurus picturatus, in western Portugal: microscopic gonad analysis reveals indeterminate fecundity and skipped spawning patterns. Zool Stud 61:41. doi:10.6620/ZS.2022.61-41.1810-522Xhttp://hdl.handle.net/10400.8/8739This study was partially supported by the European Maritime and Fisheries Fund MAR2020 project “VALOREJET: Valorização de espécies rejeitadas e de baixo valor comercial”, MAR- 01.03.01-FEAMP-0003 and by Fundação para a Ciência e Tecnologia through research contracts attributed to Vera Sequeira (CEECIND/02705/2017) and Ana Rita Vieira (CEECIND/01528/2017) and strategic project UIBD/04292/2020.Blue jack mackerel, Trachurus picturatus, is the fifth most landed fish species in mainland Portugal, but information on its reproductive biology is scarce. From September 2018 to August 2019, 626 specimens were collected from commercial vessels to clarify the reproductive strategy of the T. picturatus population off the west coast of Portugal. The proportion and length range of males and females were similar. Only three of the specimens collected were categorized as immature, indicating that the fish caught in the fishery are primarily mature. The spawning season lasted from late January until the end of March, with gonadosomatic indices being similar for males and females. Fecundity was indeterminate, and estimated batch fecundity ranged between 6,798 (at 25.4 cm TL) and 302,358 oocytes (at 33.8 cm TL). The low number of females showing direct evidence of imminent or recent spawning suggests a low number of spawning events. In addition, 12.7% of females were considered non-reproductive due to ovary abnormalities including parasitic infection by Kudoa species, atretic structures and skipped spawning events. This study highlights the importance of accounting for skipped spawning events and ovary abnormalities in the management of species fisheries.engCarangidaeLow-valued fishSkipped spawningFecundityPortugaljournal article10.6620/ZS.2022.61-41