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Caragobius urolepisexhibits vital ecological plasticity, living in brackish and freshwater habitats, including the Vietnamese Mekong Delta (VMD). Our observation revealed a notable decline in individual fish per catch due to the increased demands for food supply, which highlights the necessity of effective strategies to ensure long-term fish conservation. This study provided detailed information on testicular traits, sperm-releasing season, and length at first maturity of C. urolepisbased on a collection of 354 specimens caught monthly through trawl nets at Dong Hai (Bac Lieu) and Dam Doi (Ca Mau). After dissection, testes were weighed for the determination of gonadosomatic index (GSI) and spawning pattern. Four developmental stages were detected. Analysis of the frequency of occurrence of mature testes and GSI revealed that the sperm-releasing season of C. urolepiswas during wet months (with peaks in July, September, and November). The fish first matured at 18.0 cm in Bac Lieu and 18.7 cm in Ca Mau. The findings provided valuable insights for exploiting this species as a wild resource and may contribute to research on artificial reproduction. The study suggests avoiding the exploitation of this fish species during the spawning season to ensure future sustainable exploitation.

Glossogobius sparsipapillusis a potential candidate for aquaculture in the Mekong Delta, but information on its food and feeding habit is still fragmented and deficient. This study, therefore, aims to contribute diet and feeding ecology to this fish based on 661 specimens (331 males and 330 females) caught in estuarine areas from December 2019 to November 2020. Data analysis showed that fish diet composition comprised five categories such as Acetesspp., small fish, Polychaeta, Ucaspp., and others (e.g., fish scales and detritus). This goby is a generalist feeder, feeding preliminarily on Acetesspp. but rarely on Polychaeta. Feeding intensity is high and does not change with sexes but varies according to fish sizes, seasons, and sites. Moreover, a similar meal size was observed in different sexes, fish sizes, seasons, and sites. The findings supply the fundamental knowledge on the food and feeding of this species, being used for artificially cultivating study.