Reproductive cycle of Aplodinotus grunniens females (Rafinesque, 1819) in the Usumacinta River, Mexico

The freshwater drum Aplodinotus grunniens is a species widely distributed in North America. In the Mexican southeast, this species occurs in the Usumacinta River, where it supports an artisanal fishery. In this regard, the present study was conducted to supply detailed information on the female reproductive cycle of this species. Calculations of gonadosomatic (GSI) and hepatosomatic (HSI) indexes, histological and visual staging of ovaries as well as the staging of oocyte development were applied together to determine the reproductive changes during an annual cycle. The histological analysis revealed the presence of spawning capable females throughout the year, and the distribution frequencies of oocyte diameters displayed the continuous occurrence of mature oocytes, with great data dispersion and different modal groups. These observations were further corroborated by the presence of alternating peaks and drops in the GSI and HSIs, which were correlated with the occurrence of maturing and spawned females. These data, taken together, reveal that A. grunniens from the Usumacinta River is a partial spawner with asynchronous ovarian development and undetermined fecundity that reproduces year-round, but with spawning occurring preferably during the rainfallflooding season (June to November). The Usumacinta River seems to be a permanently favorable environment for sheltering, feeding and growth of A. grunniens broods, especially during the flooding season. The information generated in this study will be useful for the development of management strategies in the wild as well as for the exploration of A. grunniens as a potential species for aquaculture production in southern Mexico.