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The present study contributes information to the testicular development and reproductive aspects of Glossogobius giuris (Hamilton 1822), one of the target fishes in the Mekong Delta. Trawl nets were used to monthly collect fish specimens from January to December 2020 in four sites along Bassac River, from Cai Rang, Can Tho (CRCT) to Long Phu, Soc Trang (LPST), Hoa Binh, Bac Lieu (HBBL) and Dam Doi, Ca Mau (DDCM). Data analysis of 632 Glossogobius giuris individuals showed that five-stage of sperm development was found in testis histological slides. At stage IV of the testis, different phases of the sperm were observed, indicating that it is a multi-spawner, releasing sperms many times during the breeding season. Further analyses of the testis about apparent frequency and gonadosomatic index showed that this goby can release sperms monthly with a peak in the main wet season. The length at first maturity was observed at 7.24, 7.18, 7.43, and 6.57 cm of TL in CRCT, LPST, HBBL, and DDCM, respectively. The findings contribute essential information to fish population management and sustainable exploitation.

Glossogobius sparsipapillus is one of the gobies that inhabits brackish and freshwater regions in the Mekong Delta. However, data on the biological parameters of this species population are limited. Therefore, the present study aims to provide the necessary knowledge on the fishing status of this goby living in freshwater (Cai Rang, Can Tho: CR) and brackish water regions (Long Phu, Soc Trang: LP). Data analysis results of 1379 individuals showed that males outnumbered females in LP (374 males: 288 females); the reverse case was found in CR (351 males: 366 females). There were five-six classes of length frequency, with the highest values between 8 and 12 cm (1122 individuals, 81.36%). The von Bertalanffy curve was L = 15.75(1 − e−0.62(t + 0.30)) in CR and L = 15.85(1 − e−0.83(t + 0.23)) in LP. Its longevity was 4.84 yrs in CR and 3.61 yrs in LP. The growth performance was 2.19 in CR and 2.32 in LP. The total, natural, and fishing mortalities were 2.17 yr−1, 1.49 yr−1, and 0.68 yr−1 in CR; 3.46 yr−1, 1.68 yr−1, and 1.78 yr−1 in LP, respectively. The fish stock has not been overexploited as E (0.31 in CR and 0.51 in LP) were lower than E0.1 (0.465 in CR and 0.652 in LP) 0.3.46 yr−1, 1.68 yr−1, and 1.78 yr−1 in LP, respectively. The fish stock has not been overexploited as E (0.31 in CR and 0.51 in LP) were lower than E0.1 (0.465 in CR and 0.652 in LP).

This study supplies knowledge on the reproductive traits of Glossogobius aureus, one of the commercial fishes living in brackish water and freshwater. A collection of 742 G. aureus specimens was caught using gill nets from January to December 2020. The results of the gonadal breeding frequency and gonadosomatic indices showed that G. aureus spawned year-round, but with higher activity during four months, from August to October, of the wet season. Size at first maturity (Lm) of males was higher than that of females in all study sites. The batch fecundity (F) was 1044–27,349 eggs/female and increased with fish size, as shown by the high determination values (r2 > 0.6). The study results provide new references on the reproductive biology of the population of Glossogobius aureus which will help in the sustainable management of its fisheries in the studied areas.

Glossogobius aureus (Gobiiformes: Gobiidae) is a target fish and widely distributed in the Mekong Delta, from fresh to brackish waters. However, knowledge on its food and feeding ecology is scarce. Therefore, this research was carried out in four sampling sites along the estuarine of Hau River in order to fill this information gap. A total of 742 individual fish was collected monthly using trawl nets from January to December 2020. A combined analysis of the fullness index and Costello graph suggested that this fish species displayed high feeding intensity. The results revealed that G. aureus is a carnivore and its food composition comprised Acetes spp., Actinopterygii, zooplankton, and other preys (e.g. snails and detritus). Acetes spp. is the main food of this species. The diet composition varied with sites but not genders, fish sizes, and seasons. Acetes spp., Actinopterygii and other preys contributed to the spatial variation of food composition. The findings revealed knowledge about the fish feeding ecology, which may propose suitable foods for its aquaculture development.

Periophthalmus chrysospilos is an amphibious fish and considered candidates of typical aquarium fish in the Mekong Delta (MD), Vietnam. It is a species that is facing overfishing. Unfortunately, the data on its length-weight relationship (LWR), growth pattern, and condition factor are limited. The present study lasted from April 2020 to March 2021 to contribute knowledge of these data. A collection of 1,031 specimens (508 females and 523 males) was obtained from estuarine and coastal regions. The results showed that the fish total length (TL) and weight (W) were significantly different between sexes, seasons, and sites. In order to determine LWRs, weights of males and females in two sizes, seasons, four sites, and twelve months were estimated from the fish given lengths. The species displayed temporal variation in growth patterns as b values ranged from 2.87 ± 0.12 SE to 3.46 ± 0.07 SE. It generally showed positive allometric growth as b (3.22 ± 0.02 SE) was higher than the threshold of three. The fish body conditional factor was close to the well-being value of one and was not influenced by sex, but by season, site and month variations. The findings concluded that the species was well adapted to its habitat.

Glossogobius sparsipapillus is 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 Acetes spp., small fish, Polychaeta, Uca spp., and others (e.g., fish scales and detritus). This goby is a generalist feeder, feeding preliminarily on Acetes spp. 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.