Morphometrics allometry changes and sexual dimorphism in Caragobius urolepis (Gobiiformes: Gobiidae)

The present study reported an alternative way of sex-determining for scaleless worm goby Caragobius urolepis based on the regression relationship of some morphological parameters. A total of 328 samples were collected at the trawl nets in two coastal regions in Bac Lieu and Ca Mau from April to August 2022. After collection, the samples were transported to the laboratory in order to measure the total length (TL), body height (BD), head length (HL), the distance of eye (DE), and mouth width (MD) before surgery for accurate sex determination based on gonads. Regression analysis results of TL-BD (growth pattern A+ in females and I in males), TL-HL (growth pattern A+ in females and A- in males), and TL- MD (growth pattern A- in females and A+ in males) could be used to determine the sex of this fish. Moreover, TL-DE and TL-BD could be used to estimate when the samples were collected, e.g , in the dry or wet season, because DE and BD displayed A+ in the wet season but A- in the dry one. The findings could be used as an alternative way to determine fish sex and catching season for this species and others in the Mekong Delta

The effect of crab burrows on soil‐water dynamics in mangroves

Many mangrove ecosystem services, such as carbon sequestration, are closely linked to mangrove soil water content, which in turn is thought to depend on animal burrow density and the properties of the sediment in which the burrows are constructed. We measured the water content in the sediment matrix between crab burrows across 26 plots in a typical, fine-grained (clay), mangrove soil in the Mekong Delta, Vietnam. We found that the water content of the sediment matrix remained more or less constant throughout the tidal cycle, and was independent of burrow density. Our results suggest that there is little exchange of water between the burrows and the associated sediment matrix and that burrows act as an independent pipe network transporting water through the mangrove soil. To check and extend our findings, we used a numerical groundwater model to simulate an idealised burrow in a range of sediment types. The model results confirmed that fine-grained mangrove sediments do not drain readily into adjacent animal burrows because of their very low permeability. Our results have important implications for understanding and forecasting mangrove carbon dynamics with sea level rise