Ovarian traits, spawning pattern and season, length at first maturity, and batch fecundity of Caragobius urolepis (Bleeker, 1852) caught from the Vietnamese Mekong Delta

<i>Caragobius urolepis</i> has a wide range of distribution, from brackish to freshwater water, ranging from India to the Philippines and Fiji, including the Vietnamese Mekong Delta (VMD), where it lives mainly in the coastal regions and plays a vital role in food supply. Our preliminary observation showed that its population tended to decline, but little is known about this species. This study, therefore, was conducted to provide data on the ovarian structure, spawning pattern and season, length at first maturity, and batch fecundity of this fish. The study of 306 specimens caught with trawl nets from April 2022 to March 2023 in two coastal areas of VMD-Dong Hai, Bac Lieu (DHBL), and Dam Doi, Ca Mau (DDCM)-showed that this goby spawned more than once because the oocytes in stage IV ovary showed different stages of development. It could release eggs monthly during a 12-month study, with a peak in July-September since stage IV ovaries were found monthly during the study period and the GSI exhibited a high value in July-September. The fish length at first maturity and batch fecundity varied with the site, as they were 18.8 cm and 3,757-9,187 (6,142 ± 707 SE eggs/female) in DDCM and 20.5 cm and 3,760-11,118 (5,634 ± 750 SE eggs/female) in DHBL. The findings provide valuable foundations for exploiting their resources and serve as a basis for studying artificial reproduction. It is suggested to avoid catching these fish species during the breeding season to ensure sustainable exploitation in the future.